1
|
Mallick B, Saha D, Datta A, Ganguly S. Noninvasive and Contactless Characterization of Electronic Properties at the Semiconductor/Dielectric Interface Using Optical Second-Harmonic Generation. ACS Appl Mater Interfaces 2023; 15:38888-38900. [PMID: 37539844 DOI: 10.1021/acsami.3c04985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Optical second-harmonic generation (SHG) is a reliable technique for probing material surface and interface characteristics. Here, we have demonstrated a non-destructive, contactless SHG-based semiconductor/dielectric interface characterization method to measure the conduction band offset and quantitatively evaluate charge densities at the interface in oxide and at the oxide surface. This technique extracts the interface-trapped charge type (donor/acceptor) and qualitatively analyzes the process-induced variation in interface states (Dit), oxide, and oxide surface state density. These qualitative and quantitative analyses provide us with a glimpse into the band bending. The metrology method is validated through a detailed characterization of the Si/HfO2 interface. An optical setup has been developed to monitor the time-dependent second-harmonic generation (TDSHG) from the semiconductor/oxide interface. The temporal characteristics of TDSHG are explained with its relationship to the filling of Dit and spatio-temporal trapping of photoexcited charge in oxide and at the oxide surface. A numerical solver, based on plausible carrier dynamics, is used to model the experimental data and to extract the electronic properties at the Si/HfO2 interface.
Collapse
Affiliation(s)
- Binit Mallick
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Dipankar Saha
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Anindya Datta
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Swaroop Ganguly
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| |
Collapse
|
2
|
Morgan TA, Rudie J, Zamani-Alavijeh M, Kuchuk AV, Orishchin N, Alema F, Osinsky A, Sleezer R, Salamo G, Ware ME. Band Offsets of the MOCVD-Grown β-(Al 0.21Ga 0.79) 2O 3/β-Ga 2O 3 (010) Heterojunction. ACS Appl Mater Interfaces 2022; 14:33944-33951. [PMID: 35848769 DOI: 10.1021/acsami.2c04177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The band offsets for the β-(Al0.21Ga0.79)2O3/β-Ga2O3 (010) heterojunction have been experimentally measured by X-ray photoelectron spectroscopy. High-quality β-(Al0.21Ga0.79)2O3 films were grown by metal-organic chemical vapor deposition for characterization. The indirect band gap of β-(Al0.21Ga0.79)2O3 was determined by optical transmission to be 4.69 ± 0.03 eV with a direct transition of 5.37 ± 0.03 eV, while β-Ga2O3 was confirmed to have an indirect band gap of 4.52 ± 0.03 eV with a direct transition of 4.94 ± 0.03 eV. The resulting band alignment at the heterojunction was determined to be of type II with the valence and conduction band edges of β-(Al0.21Ga0.79)2O3 being -0.26 ± 0.08 and 0.43 ± 0.08 eV, respectively, above those of β-Ga2O3 (010). These values can now be used to help better design and predict the performance of β-(AlxGa1-x)2O3 heterojunction-based devices.
Collapse
Affiliation(s)
- Timothy A Morgan
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
- Naval Surface Warfare Center Crane, 300 HWY 361, Crane, Indiana 47522, United States
| | - Justin Rudie
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
| | - Mohammad Zamani-Alavijeh
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
- Physics Department, University of Arkansas, 835 W Dickson Street, Fayetteville, Arkansas 72701, United States
| | - Andrian V Kuchuk
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
| | - Nazar Orishchin
- Agnitron Technology Incorporated, Chanhassen, Minnesota 55317, United States
| | - Fikadu Alema
- Agnitron Technology Incorporated, Chanhassen, Minnesota 55317, United States
| | - Andrei Osinsky
- Agnitron Technology Incorporated, Chanhassen, Minnesota 55317, United States
| | - Robert Sleezer
- Twin Cities Engineering, Minnesota State University, Mankato, 9700 France Avenue, Suite P0820, Bloomington, Minnesota 55431, United States
| | - Gregory Salamo
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
| | - Morgan E Ware
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W Dickson Street, Fayetteville, Arkansas 72701, United States
- Department of Electrical Engineering, University of Arkansas, 4183 Bell Engineering Center, Fayetteville, Arkansas 72701, United States
| |
Collapse
|
3
|
Malevich VL, Ziaziulia PA, Norkus R, Pačebutas V, Nevinskas I, Krotkus A. Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents. Sensors (Basel) 2021; 21:s21124067. [PMID: 34204838 PMCID: PMC8231523 DOI: 10.3390/s21124067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/08/2021] [Accepted: 06/09/2021] [Indexed: 11/16/2022]
Abstract
Terahertz radiation pulses emitted after exciting semiconductor heterostructures by femtosecond optical pulses were used to determine the electron energy band offsets between different constituent materials. It has been shown that when the photon energy is sufficient enough to excite electrons in the narrower bandgap layer with an energy greater than the conduction band offset, the terahertz pulse changes its polarity. Theoretical analysis performed both analytically and by numerical Monte Carlo simulation has shown that the polarity inversion is caused by the electrons that are excited in the narrow bandgap layer with energies sufficient to surmount the band offset with the wide bandgap substrate. This effect is used to evaluate the energy band offsets in GaInAs/InP and GaInAsBi/InP heterostructures.
Collapse
Affiliation(s)
- Vitaly Leonidovich Malevich
- Stepanov Institute of Physics, National Academy of Science, Nezavisimosti Avenue 68, 220072 Minsk, Belarus;
- Belarusian State University of Informatics and Radioelectronics, P. Browki Str. 6, 220013 Minsk, Belarus
| | | | - Ričardas Norkus
- Center for Physical Sciences and Technology, Sauletekio av. 3, LT-10257 Vilnius, Lithuania; (V.P.); (I.N.); (A.K.)
- Correspondence:
| | - Vaidas Pačebutas
- Center for Physical Sciences and Technology, Sauletekio av. 3, LT-10257 Vilnius, Lithuania; (V.P.); (I.N.); (A.K.)
| | - Ignas Nevinskas
- Center for Physical Sciences and Technology, Sauletekio av. 3, LT-10257 Vilnius, Lithuania; (V.P.); (I.N.); (A.K.)
| | - Arūnas Krotkus
- Center for Physical Sciences and Technology, Sauletekio av. 3, LT-10257 Vilnius, Lithuania; (V.P.); (I.N.); (A.K.)
| |
Collapse
|
4
|
Wang D, Wang Z, Liu W, Zhou J, Feng YP, Loh KP, Wu J, Wee ATS. Atomic-Level Electronic Properties of Carbon Nitride Monolayers. ACS Nano 2020; 14:14008-14016. [PMID: 32954722 DOI: 10.1021/acsnano.0c06535] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Heteroatom-doped carbon-based materials are of significance for clean energy conversion and storage because of their fascinating electronic properties, low cost, high durability, and environmental friendliness. Atomically precise fabrication of carbon-based materials with well-defined heteroatom-dopant positions and atomic-scale understanding of their atomic-level electronic properties is a challenge. Herein, we demonstrate the bottom-up on-surface synthesis of 1D and 2D monolayer carbon nitride nanostructures with precise control of the nitrogen-atom doping sites and pore sizes. We also observe an electronic band offset at the C-N heterojunction. Using high-resolution scanning tunneling microscopy, the atomic structure of the as-prepared carbon nitride nanoporous monolayers are revealed, indicating successful and precise control of the structures and N atom doping sites. Furthermore, corroborated by theoretical calculations, scanning tunneling spectroscopy measurements reveal a valence band shift of 140 meV that results in an electric field of 2.9 × 108 V m-1 at the C-N heterojunction, indicating efficient separation of the electron-hole pair at the N doping site. Our finding offers direct atomic-level insights into the local electronic structure of the heteroatom-doped carbon-based materials.
Collapse
Affiliation(s)
- Dingguan Wang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
| | - Zishen Wang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117546, Singapore
| | - Wei Liu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Jun Zhou
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117546, Singapore
| | - Kian Ping Loh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117546, Singapore
| | - Jishan Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117546, Singapore
| |
Collapse
|
5
|
Gao Y, Sun D, Jiang X, Zhao J. Ab initioanalytic calculation of point defects in AlGaN/GaN heterointerfaces. J Phys Condens Matter 2020; 33:035002. [PMID: 33007770 DOI: 10.1088/1361-648x/abbdbb] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/02/2020] [Indexed: 06/11/2023]
Abstract
One of the major challenges for the GaN-based high-electron-mobility transistors (HEMTs) used as high power devices is to understand the effect of defects, especially on the band alignment. Usingab initiocalculation, herein we investigate the variations of band offsets with interfacial structure, defect position, interface states and Al content in AlxGa1-xN/GaN heterostructures (x= 0.06, 0.13, 0.19, 0.25). It was found that N vacancy (VN) and Ga anti-site (GaN) introduce nonlocal interface states and the change of valence band offset (VBO) depends on the defect location. While the interface states induced by Ga vacancy (VGa) and N anti-site (NGa) show strong localization behavior, and their impact on VBO is independent on the defect position. The low symmetry of wurtzite nitride and the lattice mismatch between AlGaN and GaN will generate polarization charge (spontaneous polarization and piezoelectric polarization) at the interface. Along the direction of polarization field, VNand GaNlying in the AlGaN side change the VBO most pronouncedly. These theoretical results provide useful guidance for control of point defects in AlGaN/GaN HEMTs, which have profound impact on the performance and reliability of GaN-based devices.
Collapse
Affiliation(s)
- Yinlu Gao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), Dalian University of Technology, Dalian 116024, People's Republic of China
| | - Dan Sun
- Science and Technology on Reactor System Design Technology Laboratory, Nuclear Power Institute of China, Chengdu, 610213, People's Republic of China
| | - Xue Jiang
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), Dalian University of Technology, Dalian 116024, People's Republic of China
| | - Jijun Zhao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), Dalian University of Technology, Dalian 116024, People's Republic of China
| |
Collapse
|
6
|
Rondiya S, Jadhav Y, Dzade NY, Ahammed R, Goswami T, De Sarkar A, Jadkar S, Haram S, Ghosh HN. Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu 2Zn 1-x Cd x SnS 4 Heterointerface for Photovoltaic Applications. ACS Appl Energy Mater 2020; 3:5153-5162. [PMID: 32905359 PMCID: PMC7469238 DOI: 10.1021/acsaem.9b02314] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 05/05/2020] [Indexed: 05/14/2023]
Abstract
To improve the constraints of kesterite Cu2ZnSnS4 (CZTS) solar cell, such as undesirable band alignment at p-n interfaces, bandgap tuning, and fast carrier recombination, cadmium (Cd) is introduced into CZTS nanocrystals forming Cu2Zn1-x Cd x SnS4 through cost-effective solution-based method without postannealing or sulfurization treatments. A synergetic experimental-theoretical approach was employed to characterize and assess the optoelectronic properties of Cu2Zn1-x Cd x SnS4 materials. Tunable direct band gap energy ranging from 1.51 to 1.03 eV with high absorption coefficient was demonstrated for the Cu2Zn1-x Cd x SnS4 nanocrystals with changing Zn/Cd ratio. Such bandgap engineering in Cu2Zn1-x Cd x SnS4 helps in effective carrier separation at interface. Ultrafast spectroscopy reveals a longer lifetime and efficient separation of photoexcited charge carriers in Cu2CdSnS4 (CCTS) nanocrystals compared to that of CZTS. We found that there exists a type-II staggered band alignment at the CZTS (CCTS)/CdS interface, from cyclic voltammetric (CV) measurements, corroborated by first-principles density functional theory (DFT) calculations, predicting smaller conduction band offset (CBO) at the CCTS/CdS interface as compared to the CZTS/CdS interface. These results point toward efficient separation of photoexcited carriers across the p-n junction in the ultrafast time scale and highlight a route to improve device performances.
Collapse
Affiliation(s)
- Sachin
R. Rondiya
- Institute
of Nano Science and Technology, Mohali, Punjab 160062, India
| | - Yogesh Jadhav
- Department
of Chemistry, Savitribai Phule Pune University, Pune 411007, India
| | - Nelson Y. Dzade
- School
of Chemistry, Cardiff University, Cardiff, CF10 3AT, Wales United Kingdom
| | - Raihan Ahammed
- Institute
of Nano Science and Technology, Mohali, Punjab 160062, India
| | - Tanmay Goswami
- Institute
of Nano Science and Technology, Mohali, Punjab 160062, India
| | - Abir De Sarkar
- Institute
of Nano Science and Technology, Mohali, Punjab 160062, India
| | - Sandesh Jadkar
- Department
of Physics, Savitribai Phule Pune University, Pune 411007, India
| | - Santosh Haram
- Department
of Chemistry, Savitribai Phule Pune University, Pune 411007, India
| | - Hirendra N. Ghosh
- Institute
of Nano Science and Technology, Mohali, Punjab 160062, India
- E-mail: . Phone: +91-172-2210075/57/56 ext. 120. Fax: +91-172-2211074
| |
Collapse
|
7
|
Qu Z, Su Y, Sun L, Liang F, Zhang G. Study of the Structure, Electronic and Optical Properties of BiOI/Rutile-TiO 2 Heterojunction by the First-Principle Calculation. Materials (Basel) 2020; 13:E323. [PMID: 31936752 PMCID: PMC7014688 DOI: 10.3390/ma13020323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/02/2020] [Accepted: 01/06/2020] [Indexed: 11/16/2022]
Abstract
Using the first-principle calculation that is based on the density functional theory (DFT), our group gains some insights of the structural, electronic and optical properties of two brand new types of BiOI/TiO2 heterojunctions: 1I-terminated BiOI {001} surface/TiO2 (1I-BiOI/TiO2) and BiO-terminated BiOI {001} surface/TiO2 (BiO-BiOI/TiO2). The calculation illustrates that BiOI/TiO2 heterojunction has excellent mechanical stability, and it shows that there is a great possibility for the BiOI/TiO2 heterojunction to be used in visible-light range, hence the photocatalytic ability can be enhanced dramatically. Especially, from the calculation, we discovered that there are two specific properties: the band-gap of 1I-BiOI/TiO2 heterojunction reduces to 0.28 eV, and the BiO-BiOI/TiO2 semiconductor material changes to n-type. The calculated band offset (BOs) for 1I-BiOI/TiO2 heterojunction indicates that the interfacial structure contributes a lot to a suitable band alignment which can disperse the photo-generated carriers into the opposite sides of the interface, so this could effectively weaken the electron-hole recombination. Meanwhile, the built-in potential around the interface accelerates the movement of the photo-generated electron-hole pairs. We believe this is the reason that the BiOI/TiO2 material shows perfect photocatalytic performance. This paper can provide theoretical support for the related research, especially the further research of the BiOI-based material.
Collapse
Affiliation(s)
- Zhan Qu
- School of Microelectronics, Xi’an Jiaotong University, Xi’an 710049, China; (Z.Q.); (L.S.)
| | - Yali Su
- School of Mechanical Engineering, Xi’an Shiyou University, Xi’an 710065, China;
| | - Li Sun
- School of Microelectronics, Xi’an Jiaotong University, Xi’an 710049, China; (Z.Q.); (L.S.)
| | - Feng Liang
- School of Microelectronics, Xi’an Jiaotong University, Xi’an 710049, China; (Z.Q.); (L.S.)
| | - Guohe Zhang
- School of Microelectronics, Xi’an Jiaotong University, Xi’an 710049, China; (Z.Q.); (L.S.)
| |
Collapse
|
8
|
Lou X, Gong X, Feng J, Gordon R. Band-Offset Analysis of Atomic Layer Deposition La 2O 3 on GaAs(111), (110), and (100) Surfaces for Epitaxial Growth. ACS Appl Mater Interfaces 2019; 11:28515-28519. [PMID: 31294539 DOI: 10.1021/acsami.9b08436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this paper, we measured band offsets for La2O3 prepared by atomic layer deposition on GaAs(111), (110), and (100) surfaces. La2O3 grows epitaxially on GaAs(111) with very low interfacial defect density and exhibits a band offset that is predicted for defect-free interfaces by the metal-induced gap state theory. On the other hand, the polycrystalline La2O3 deposited on GaAs(110) and (100) shows band offsets close to the values predicted for Fermi-level pinning. In this way, band offsets can qualitatively estimate interfacial defect levels.
Collapse
|
9
|
Gao Z, Zhou Z, Tománek D. Degenerately Doped Transition Metal Dichalcogenides as Ohmic Homojunction Contacts to Transition Metal Dichalcogenide Semiconductors. ACS Nano 2019; 13:5103-5111. [PMID: 31038922 DOI: 10.1021/acsnano.8b08190] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In search of an improved strategy to form low-resistance contacts to MoS2 and related semiconducting transition metal dichalcogenides, we use ab initio density functional electronic structure calculations in order to determine the equilibrium geometry and electronic structure of MoO3/MoS2 and MoO2/MoS2 bilayers. Our results indicate that, besides a rigid band shift associated with charge transfer, the presence of molybdenum oxide modifies the electronic structure of MoS2 very little. We find that the charge transfer in the bilayer provides a sufficient degree of hole doping to MoS2, resulting in a highly transparent contact region.
Collapse
Affiliation(s)
- Zhibin Gao
- Physics and Astronomy Department , Michigan State University , East Lansing , Michigan 48824 , United States
- Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering , Tongji University , 200092 Shanghai , People's Republic of China
| | - Zhixian Zhou
- Physics and Astronomy Department , Wayne State University , Detroit , Michigan 48201 , United States
| | - David Tománek
- Physics and Astronomy Department , Michigan State University , East Lansing , Michigan 48824 , United States
- Mandelstam Institute for Theoretical Physics and School of Physics , University of the Witwatersrand , 2050 Johannesburg , South Africa
| |
Collapse
|
10
|
Hudait MK, Clavel M, Liu JS, Ghosh A, Jain N, Bodnar RJ. Transport Across Heterointerfaces of Amorphous Niobium Oxide and Crystallographically Oriented Epitaxial Germanium. ACS Appl Mater Interfaces 2017; 9:43315-43324. [PMID: 29144722 DOI: 10.1021/acsami.7b06601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Because of the high carrier mobility of germanium (Ge) and high dielectric permittivity of amorphous niobium pentoxide (a-Nb2O5), Ge/a-Nb2O5 heterostructures offer several advantages for the rapidly developing field of oxide-semiconductor-based multifunctional devices. To this end, we investigate the growth, structural, band alignment, and metal-insulator-semiconductor (MIS) electrical properties of physical vapor-deposited Nb2O5 on crystallographically oriented (100), (110), and (111)Ge epilayers. The as-deposited Nb2O5 dielectrics were found to be in the amorphous state, demonstrating an abrupt oxide/semiconductor heterointerface with respect to Ge, when examined via low- and high-magnification cross-sectional transmission electron microscopy. Additionally, variable-angle spectroscopic ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to independently determine the a-Nb2O5 band gap, yielding a direct gap value of 4.30 eV. Moreover, analysis of the heterointerfacial energy band alignment between a-Nb2O5 and epitaxial Ge revealed valance band offsets (ΔEV) greater than 2.5 eV, following the relation ΔEV(111) > ΔEV(110) > ΔEV(100). Similarly, utilizing the empirically determined a-Nb2O5 band gap, conduction band offsets (ΔEC) greater than 0.75 eV were found, likewise following the relation ΔEC(110) > ΔEC(100) > ΔEC(111). Leveraging the reduced ΔEC observed at the a-Nb2O5/Ge heterointerface, we also perform the first experimental investigation into Schottky barrier height reduction on n-Ge using a 2 nm a-Nb2O5 interlayer, resulting in a 20× increase in reverse-bias current density and improved Ohmic behavior.
Collapse
Affiliation(s)
- Mantu K Hudait
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Michael Clavel
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Jheng-Sin Liu
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Aheli Ghosh
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Nikhil Jain
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| | - Robert J Bodnar
- Advanced Devices & Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering and ‡Fluids Research Laboratory, Department of Geosciences, Virginia Tech , Blacksburg, Virginia 24061, United States
| |
Collapse
|
11
|
Zhang KHL, Wu R, Tang F, Li W, Oropeza FE, Qiao L, Lazarov VK, Du Y, Payne DJ, MacManus-Driscoll JL, Blamire MG. Electronic Structure and Band Alignment at the NiO and SrTiO 3 p-n Heterojunctions. ACS Appl Mater Interfaces 2017; 9:26549-26555. [PMID: 28695740 DOI: 10.1021/acsami.7b06025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Understanding the energetics at the interface, including the alignment of valence and conduction bands, built-in potentials, and ionic and electronic reconstructions, is an important challenge in designing oxide interfaces that have controllable multifunctionalities for novel (opto-)electronic devices. In this work, we report detailed investigations on the heterointerface of wide-band-gap p-type NiO and n-type SrTiO3 (STO). We show that despite a large lattice mismatch (∼7%) and dissimilar crystal structure, high-quality NiO and Li-doped NiO (LNO) thin films can be epitaxially grown on STO(001) substrates through a domain-matching epitaxy mechanism. X-ray photoelectron spectroscopy studies indicate that NiO/STO heterojunctions form a type II "staggered" band alignment. In addition, a large built-in potential of up to 0.97 eV was observed at the interface of LNO and Nb-doped STO (NbSTO). The LNO/NbSTO p-n heterojunctions exhibit not only a large rectification ratio of 2 × 103 but also a large ideality factor of 4.3. The NiO/STO p-n heterojunctions have important implications for applications in photocatalysis and photodetectors as the interface provides favorable energetics for facile separation and transport of photogenerated electrons and holes.
Collapse
Affiliation(s)
- Kelvin H L Zhang
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Rui Wu
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Fengzai Tang
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Weiwei Li
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Freddy E Oropeza
- Department of Materials, Imperial College London , Exhibition Road, London SW7 2AZ, U.K
| | - Liang Qiao
- School of Materials, The University of Manchester , Manchester M13 9PL, U.K
| | - Vlado K Lazarov
- Department of Physics, University of York , Heslington, York YO10 5DD, U.K
| | - Yingge Du
- Physical Sciences Division, Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory , Richland, Washington 99352, United States
| | - David J Payne
- Department of Materials, Imperial College London , Exhibition Road, London SW7 2AZ, U.K
| | - Judith L MacManus-Driscoll
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| | - Mark G Blamire
- Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
| |
Collapse
|
12
|
Abstract
Recent experimental investigations have confirmed the possibility to synthesize and exploit polytypism in group IV nanowires. Driven by this promising evidence, we use first-principles methods based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties of hexagonal-diamond and cubic-diamond Si NWs as well as their homojunctions. We show that hexagonal-diamond NWs are characterized by a more pronounced quantum confinement effect than cubic-diamond NWs. Furthermore, they absorb more light in the visible region with respect to cubic-diamond ones and, for most of the studied diameters, they are direct band gap materials. The study of the homojunctions reveals that the diameter has a crucial effect on the band alignment at the interface. In particular, at small diameters the band-offset is type-I whereas at experimentally relevant sizes the offset turns up to be of type-II. These findings highlight intriguing possibilities to modulate electron and hole separations as well as electronic and optical properties by simply modifying the crystal phase and the size of the junction.
Collapse
Affiliation(s)
| | | | | | - Maurizia Palummo
- Dipartimento di Fisica, Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Roma, Italy
- INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati, Italy
| | - Riccardo Rurali
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de Bellaterra , 08193 Bellaterra, Barcelona, Spain
| |
Collapse
|
13
|
Siol S, Hellmann JC, Tilley SD, Graetzel M, Morasch J, Deuermeier J, Jaegermann W, Klein A. Band Alignment Engineering at Cu2O/ZnO Heterointerfaces. ACS Appl Mater Interfaces 2016; 8:21824-31. [PMID: 27452037 DOI: 10.1021/acsami.6b07325] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Energy band alignments at heterointerfaces play a crucial role in defining the functionality of semiconductor devices, yet the search for material combinations with suitable band alignments remains a challenge for numerous applications. In this work, we demonstrate how changes in deposition conditions can dramatically influence the functional properties of an interface, even within the same material system. The energy band alignment at the heterointerface between Cu2O and ZnO was studied using photoelectron spectroscopy with stepwise deposition of ZnO onto Cu2O and vice versa. A large variation of energy band alignment depending on the deposition conditions of the substrate and the film is observed, with valence band offsets in the range ΔEVB = 1.45-2.7 eV. The variation of band alignment is accompanied by the occurrence or absence of band bending in either material. It can therefore be ascribed to a pinning of the Fermi level in ZnO and Cu2O, which can be traced back to oxygen vacancies in ZnO and to metallic precipitates in Cu2O. The intrinsic valence band offset for the interface, which is not modified by Fermi level pinning, is derived as ΔEVB ≈ 1.5 eV, being favorable for solar cell applications.
Collapse
Affiliation(s)
- Sebastian Siol
- Technische Universität Darmstadt , Institute of Materials Science, Surface Science Division, Petersenstrasse 32, 64287 Darmstadt, Germany
| | - Jan C Hellmann
- Technische Universität Darmstadt , Institute of Materials Science, Surface Science Division, Petersenstrasse 32, 64287 Darmstadt, Germany
| | - S David Tilley
- Ecole Polytechnique Fédérale de Lausanne (EPFL) , Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Station 6, CH-1015 Lausanne, Switzerland
| | - Michael Graetzel
- Ecole Polytechnique Fédérale de Lausanne (EPFL) , Institut des Sciences et Ingénierie Chimiques, Laboratory of Photonics and Interfaces, Station 6, CH-1015 Lausanne, Switzerland
| | - Jan Morasch
- Technische Universität Darmstadt , Institute of Materials Science, Surface Science Division, Petersenstrasse 32, 64287 Darmstadt, Germany
| | - Jonas Deuermeier
- i3N/CENIMAT, Universidade NOVA de Lisboa and CEMOP/UNINOVA , Department of Materials Science, Faculty of Science and Technology, Campus de Caparica, 2829-516 Caparica, Portugal
| | - Wolfram Jaegermann
- Technische Universität Darmstadt , Institute of Materials Science, Surface Science Division, Petersenstrasse 32, 64287 Darmstadt, Germany
| | - Andreas Klein
- Technische Universität Darmstadt , Institute of Materials Science, Surface Science Division, Petersenstrasse 32, 64287 Darmstadt, Germany
| |
Collapse
|
14
|
Bär M, Barreau N, Couzinié-Devy F, Weinhardt L, Wilks RG, Kessler J, Heske C. Impact of Annealing-Induced Intermixing on the Electronic Level Alignment at the In2S3/Cu(In,Ga)Se2 Thin-Film Solar Cell Interface. ACS Appl Mater Interfaces 2016; 8:2120-2124. [PMID: 26716913 DOI: 10.1021/acsami.5b10614] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The interface between a nominal In2S3 buffer and a Cu(In,Ga)Se2 (CIGSe) thin-film solar cell absorber was investigated by direct and inverse photoemission to determine the interfacial electronic structure. On the basis of a previously reported heavy intermixing at the interface (S diffuses into the absorber; Cu diffuses into the buffer; and Na diffuses through it), we determine here the band alignment at the interface. The results suggest that the pronounced intermixing at the In2S3/CIGSe interface leads to a favorable electronic band alignment, necessary for high-efficiency solar cell devices.
Collapse
Affiliation(s)
- Marcus Bär
- Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus-Senftenberg , Platz der Deutschen Einheit 1, 03046 Cottbus, Germany
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway, Las Vegas, Nevada 89154-4003, United States
| | - Nicolas Barreau
- Institut des Matériaux Jean Rouxel (IMN)-UMR 6502, Université de Nantes, Centre National de la Recherche Scientifique (CNRS) , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
| | - François Couzinié-Devy
- Institut des Matériaux Jean Rouxel (IMN)-UMR 6502, Université de Nantes, Centre National de la Recherche Scientifique (CNRS) , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
| | - Lothar Weinhardt
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway, Las Vegas, Nevada 89154-4003, United States
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology , 76344 Eggenstein-Leopoldshafen, Germany
- Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology , Engesserstraße 18/20, 76128 Karlsruhe, Germany
| | - Regan G Wilks
- Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - John Kessler
- Institut des Matériaux Jean Rouxel (IMN)-UMR 6502, Université de Nantes, Centre National de la Recherche Scientifique (CNRS) , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
| | - Clemens Heske
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV) , 4505 Maryland Parkway, Las Vegas, Nevada 89154-4003, United States
- Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology , 76344 Eggenstein-Leopoldshafen, Germany
- Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology , Engesserstraße 18/20, 76128 Karlsruhe, Germany
| |
Collapse
|
15
|
Abstract
Using different types of WSe2 and graphene-based heterostructures, we experimentally determine the offset between the graphene neutrality point and the WSe2 conduction and valence band edges, as well as the WSe2 dielectric constant along the c-axis. In a first heterostructure, consisting of WSe2-on-graphene, we use the WSe2 layer as the top dielectric in dual-gated graphene field-effect transistors to determine the WSe2 capacitance as a function of thickness, and the WSe2 dielectric constant along the c-axis. In a second heterostructure consisting of graphene-on-WSe2, the lateral electron transport shows ambipolar behavior characteristic of graphene combined with a conductivity saturation at sufficiently high positive (negative) gate bias, associated with carrier population of the conduction (valence) band in WSe2. By combining the experimental results from both heterostructures, we determine the band offset between the graphene charge neutrality point, and the WSe2 conduction and valence band edges.
Collapse
Affiliation(s)
- Kyounghwan Kim
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Stefano Larentis
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Babak Fallahazad
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Kayoung Lee
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Jiamin Xue
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - David C Dillen
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Chris M Corbet
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| | - Emanuel Tutuc
- Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
| |
Collapse
|
16
|
Abstract
First-principles calculations are performed to explore the geometry, bonding, and electronic structures of six ultrathin photovoltaic heterostructures consisting of pristine and B- or N-doped fullerenes and MoS2 or WS2 monolayers. The fullerenes prefer to be attached with a hexagon parallel to the monolayer, where B and N favor proximity to the monolayer. The main electronic properties of the subsystems stay intact, suggesting weak interfacial interaction. Both the C60/MoS2 and C60/WS2 systems show type-II band alignments. However, the built-in potential in the former case is too small to effectively drive electron-hole separation across the interface, whereas the latter system is predicted to show good photovoltaic performance. Unfortunately, B and N doping destroys the type-II band alignment on MoS2 and preserves it only in one spin channel on WS2, which is unsuitable for excitonic solar cells. Our results suggest that the C60/WS2 system is highly promising for excitonic solar cells.
Collapse
Affiliation(s)
- Li-Yong Gan
- PSE Division, KAUST, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Qingyun Zhang
- PSE Division, KAUST, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Yingchun Cheng
- PSE Division, KAUST, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | | |
Collapse
|
17
|
Wei W, Qin Z, Fan S, Li Z, Shi K, Zhu Q, Zhang G. Valence band offset of β-Ga2O3/wurtzite GaN heterostructure measured by X-ray photoelectron spectroscopy. Nanoscale Res Lett 2012; 7:562. [PMID: 23046910 PMCID: PMC3526396 DOI: 10.1186/1556-276x-7-562] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 09/24/2012] [Indexed: 05/23/2023]
Abstract
A sample of the β-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the β-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the β-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the β-Ga2O3/GaN structure is 1.40 ± 0.08 eV.
Collapse
Affiliation(s)
- Wei Wei
- State Key Laboratory of Artificial Microstructure and Microscopic Physics, School of Physics, Peking University, Beijing, 100871, People's Republic of China
| | - Zhixin Qin
- State Key Laboratory of Artificial Microstructure and Microscopic Physics, School of Physics, Peking University, Beijing, 100871, People's Republic of China
| | - Shunfei Fan
- State Key Laboratory of Artificial Microstructure and Microscopic Physics, School of Physics, Peking University, Beijing, 100871, People's Republic of China
| | - Zhiwei Li
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing, 100083, People's Republic of China
| | - Kai Shi
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing, 100083, People's Republic of China
| | - Qinsheng Zhu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing, 100083, People's Republic of China
| | - Guoyi Zhang
- State Key Laboratory of Artificial Microstructure and Microscopic Physics, School of Physics, Peking University, Beijing, 100871, People's Republic of China
| |
Collapse
|