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Ghosh S, Sun G, Morgan TA, Forcherio GT, Cheng HH, Chang GE. Dark Current Analysis on GeSn p-i-n Photodetectors. Sensors (Basel) 2023; 23:7531. [PMID: 37687985 PMCID: PMC10490798 DOI: 10.3390/s23177531] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/11/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023]
Abstract
Group IV alloys of GeSn have been extensively investigated as a competing material alternative in shortwave-to-mid-infrared photodetectors (PDs). The relatively large defect densities present in GeSn alloys are the major challenge in developing practical devices, owing to the low-temperature growth and lattice mismatch with Si or Ge substrates. In this paper, we comprehensively analyze the impact of defects on the performance of GeSn p-i-n homojunction PDs. We first present our theoretical models to calculate various contributing components of the dark current, including minority carrier diffusion in p- and n-regions, carrier generation-recombination in the active intrinsic region, and the tunneling effect. We then analyze the effect of defect density in the GeSn active region on carrier mobilities, scattering times, and the dark current. A higher defect density increases the dark current, resulting in a reduction in the detectivity of GeSn p-i-n PDs. In addition, at low Sn concentrations, defect-related dark current density is dominant, while the generation dark current becomes dominant at a higher Sn content. These results point to the importance of minimizing defect densities in the GeSn material growth and device processing, particularly for higher Sn compositions necessary to expand the cutoff wavelength to mid- and long-wave infrared regime. Moreover, a comparative study indicates that further improvement of the material quality and optimization of device structure reduces the dark current and thereby increases the detectivity. This study provides more realistic expectations and guidelines for evaluating GeSn p-i-n PDs as a competitor to the III-V- and II-VI-based infrared PDs currently on the commercial market.
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Affiliation(s)
- Soumava Ghosh
- Department of Mechanical Engineering, and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chiayi 621301, Taiwan;
| | - Greg Sun
- Department of Engineering, University of Massachusetts—Boston, Boston, MA 02125, USA;
| | - Timothy A. Morgan
- Electro-Optic Technology Division, Naval Surface Warfare Center, Crane, IN 47522, USA; (T.A.M.); (G.T.F.)
| | - Gregory T. Forcherio
- Electro-Optic Technology Division, Naval Surface Warfare Center, Crane, IN 47522, USA; (T.A.M.); (G.T.F.)
| | - Hung-Hsiang Cheng
- Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan;
| | - Guo-En Chang
- Department of Mechanical Engineering, and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chiayi 621301, Taiwan;
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Chang GE, Yu SQ, Sun G. "GeSn Rule-23"-The Performance Limit of GeSn Infrared Photodiodes. Sensors (Basel) 2023; 23:7386. [PMID: 37687845 PMCID: PMC10490364 DOI: 10.3390/s23177386] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/10/2023] [Accepted: 08/22/2023] [Indexed: 09/10/2023]
Abstract
Group-IV GeSn photodetectors (PDs) compatible with standard complementary metal-oxide-semiconductor (CMOS) processing have emerged as a new and non-toxic infrared detection technology to enable a wide range of infrared applications. The performance of GeSn PDs is highly dependent on the Sn composition and operation temperature. Here, we develop theoretical models to establish a simple rule of thumb, namely "GeSn-rule 23", to describe GeSn PDs' dark current density in terms of operation temperature, cutoff wavelength, and Sn composition. In addition, analysis of GeSn PDs' performance shows that the responsivity, detectivity, and bandwidth are highly dependent on operation temperature. This rule provides a simple and convenient indicator for device developers to estimate the device performance at various conditions for practical applications.
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Affiliation(s)
- Guo-En Chang
- Department of Mechanical Engineering, Advanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chia-Yi 62102, Taiwan
| | - Shui-Qing Yu
- Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701, USA;
| | - Greg Sun
- Department of Engineering, University of Massachusetts-Boston, Boston, MA 02125, USA;
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Bonino V, Pauc N, Calvo V, Frauenrath M, Hartmann JM, Chelnokov A, Reboud V, Rosenthal M, Segura-Ruiz J. Microstructuring to Improve the Thermal Stability of GeSn Layers. ACS Appl Mater Interfaces 2022; 14:22270-22277. [PMID: 35510890 DOI: 10.1021/acsami.2c01652] [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: 06/14/2023]
Abstract
Tin segregation in Ge1-xSnx alloys is one of the major problems potentially hindering the use of this material in devices. Ge1-xSnx microdisks fabricated from layers with Sn concentrations up to 16.9% underwent here annealing at temperatures as high as 400 °C for 20 min without Sn segregation, in contrast with the full segregation observed in the corresponding blanket layers annealed simultaneously. After annealing, no changes in the elemental composition of the microdisks were evidenced. An enhancement of the total integrated photoluminescence, with no modifications of the emission energy, was also observed. These findings show that microstructuring offers a completely new path in maintaining the stability of high Sn concentration Ge1-xSnx layers at temperatures much higher than those used for growth. This approach enables the use of thermal annealing processes to improve the properties of this alloy in optoelectronic devices (such as light emitting diodes, lasers, photodetectors, or modulators). It should also facilitate the integration of Ge1-xSnx into well-established technologies requiring medium temperature processes. The same strategy may help to prevent Sn segregation during high temperature processes in similar metastable alloys.
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Affiliation(s)
- Valentina Bonino
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Nicolas Pauc
- University of Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, 38000 Grenoble, France
| | - Vincent Calvo
- University of Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, 38000 Grenoble, France
| | | | | | - Alexei Chelnokov
- University of Grenoble Alpes, CEA, LETI, F-38054 Grenoble, France
| | - Vincent Reboud
- University of Grenoble Alpes, CEA, LETI, F-38054 Grenoble, France
| | - Martin Rosenthal
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Jaime Segura-Ruiz
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France
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Liu S, Covian AC, Wang X, Cline CT, Akey A, Dong W, Yu SQ, Liu J. 3D Nanoscale Mapping of Short-Range Order in GeSn Alloys. Small Methods 2022; 6:e2200029. [PMID: 35373530 DOI: 10.1002/smtd.202200029] [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] [Received: 01/09/2022] [Revised: 02/25/2022] [Indexed: 06/14/2023]
Abstract
GeSn on Si has attracted much research interest due to its tunable direct bandgap for mid-infrared applications. Recently, short-range order (SRO) in GeSn alloys has been theoretically predicted, which profoundly impacts the band structure. However, characterizing SRO in GeSn is challenging. Guided by physics-informed Poisson statistical analyses of k-nearest neighbors (KNN) in atom probe tomography (APT), a new approach is demonstrated here for 3D nanoscale SRO mapping and semi-quantitative strain mapping in GeSn. For GeSn with ≈14 at. % Sn, the SRO parameters of Sn-Sn 1NN in 10 × 10 × 10 nm3 nanocubes can deviate from that of the random alloys by ±15 %. The relatively large fluctuation of the SRO parameters contributes to band-edge softening observed optically. Sn-Sn 1NN also tends to be more favored toward the surface, less favored under strain relaxation or tensile strain, while almost independent of local Sn composition. An algorithm based on least square fit of atomic positions further verifies this Poisson-KNN statistical method. Compared to existing macroscopic spectroscopy or electron microscopy techniques, this new APT statistical analysis uniquely offers 3D SRO mapping at nanoscale resolution in a relatively large volume with millions of atoms. It can also be extended to investigate SRO in other alloy systems.
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Affiliation(s)
- Shang Liu
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
| | - Alejandra Cuervo Covian
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
| | - Xiaoxin Wang
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
| | - Cory T Cline
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
| | - Austin Akey
- Center for Nanoscale Systems, Harvard University, Cambridge, MA, 02138, USA
| | - Weiling Dong
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
| | - Shui-Qing Yu
- Department of Electrical Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Jifeng Liu
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA
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Ghosh S, Lin KC, Tsai CH, Kumar H, Chen Q, Zhang L, Son B, Tan CS, Kim M, Mukhopadhyay B, Chang GE. Metal-Semiconductor-Metal GeSn Photodetectors on Silicon for Short-Wave Infrared Applications. Micromachines (Basel) 2020; 11:E795. [PMID: 32839407 DOI: 10.3390/mi11090795] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 08/19/2020] [Accepted: 08/19/2020] [Indexed: 11/17/2022]
Abstract
Metal-semiconductor-metal photodetectors (MSM PDs) are effective for monolithic integration with other optical components of the photonic circuits because of the planar fabrication technique. In this article, we present the design, growth, and characterization of GeSn MSM PDs that are suitable for photonic integrated circuits. The introduction of 4% Sn in the GeSn active region also reduces the direct bandgap and shows a redshift in the optical responsivity spectra, which can extend up to 1800 nm wavelength, which means it can cover the entire telecommunication bands. The spectral responsivity increases with an increase in bias voltage caused by the high electric field, which enhances the carrier generation rate and the carrier collection efficiency. Therefore, the GeSn MSM PDs can be a suitable device for a wide range of short-wave infrared (SWIR) applications.
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