26
|
Shen C, Lee C, Ng TK, Nakamura S, Speck JS, DenBaars SP, Alyamani AY, El-Desouki MM, Ooi BS. High-speed 405-nm superluminescent diode (SLD) with 807-MHz modulation bandwidth. OPTICS EXPRESS 2016; 24:20281-20286. [PMID: 27607634 DOI: 10.1364/oe.24.020281] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
III-nitride LEDs are fundamental components for visible-light communication (VLC). However, the modulation bandwidth is inherently limited by the relatively long carrier lifetime. In this letter, we present the 405 nm emitting superluminescent diode (SLD) with tilted facet design on semipolar GaN substrate, showing a broad emission of ~9 nm at 20 mW optical power. Owing to the fast recombination (τe<0.35 ns) through the amplified spontaneous emission, the SLD exhibits a significantly large 3-dB bandwidth of 807 MHz. A data rate of 1.3 Gbps with a bit-error rate of 2.9 × 10-3 was obtained using on-off keying modulation scheme, suggesting the SLD being a high-speed transmitter for VLC applications.
Collapse
|
27
|
Alhassan AI, Farrell RM, Saifaddin B, Mughal A, Wu F, DenBaars SP, Nakamura S, Speck JS. High luminous efficacy green light-emitting diodes with AlGaN cap layer. OPTICS EXPRESS 2016; 24:17868-17873. [PMID: 27505754 DOI: 10.1364/oe.24.017868] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate very high luminous efficacy green light-emitting diodes employing Al0.30Ga0.70N cap layer grown on patterned sapphire substrates by metal organic chemical vapor deposition. The peak external quantum efficiency and luminous efficacies were 44.3% and 239 lm/w, respectively. At 20 mA (20 A/cm2) the light output power was 14.3 mW, the forward voltage was 3.5 V, the emission wavelength was 526.6 nm, and the external quantum efficiency was 30.2%. These results are among the highest reported luminous efficacy values for InGaN based green light-emitting diodes.
Collapse
|
28
|
Bierwagen O, Rombach J, Speck JS. Faceting control by the stoichiometry influence on the surface free energy of low-index bcc-In2O3 surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:224006. [PMID: 26952816 DOI: 10.1088/0953-8984/28/22/224006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The faceting of In2O3(0 0 1), (0 1 1), and (1 1 1) grown by plasma-assisted molecular beam epitaxy on yttria-stabilised zirconia was investigated under different growth conditions-conventionally used oxygen-rich growth conditions with and without heavy Sn-doping, and indium-rich growth conditions-by in situ reflection high-energy electron diffraction, scanning electron microscopy, x-ray diffraction, and atomic force microscopy. In a simple thermodynamic model that considers surface free energy only, the observed faceting is compared to recent theoretical predictions of the surface tension (also termed surface free energy) anisotropy and the related equilibrium crystal shape derived from a Wulff construction. These predictions and our comparison include the variation with growth-condition-dependent oxygen chemical potential. Our results demonstrate how the experimentally changed oxygen chemical potential controls the faceting or island shape of In2O3 by changing the surface tension anisotropy. While the experimental results largely agree with the theoretically derived surface tension anisotropy, they strongly suggest a lower relative surface tension of the (0 0 1) surface at lower oxygen chemical potential (In-rich growth conditions) than theoretically predicted or a significant surface entropy contribution.
Collapse
|
29
|
Shen C, Ng TK, Leonard JT, Pourhashemi A, Nakamura S, DenBaars SP, Speck JS, Alyamani AY, El-Desouki MM, Ooi BS. High-brightness semipolar (2021¯) blue InGaN/GaN superluminescent diodes for droop-free solid-state lighting and visible-light communications. OPTICS LETTERS 2016; 41:2608-2611. [PMID: 27244426 DOI: 10.1364/ol.41.002608] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A high-brightness, droop-free, and speckle-free InGaN/GaN quantum well blue superluminescent diode (SLD) was demonstrated on a semipolar (2021¯) GaN substrate. The 447-nm emitting SLD has a broad spectral linewidth of 6.3 nm at an optical power of 123 mW. A peak optical power of 256 mW was achieved at 700 mA CW injection current. By combining YAG:Ce phosphor, SLD-generated white light shows a color-rendering index (CRI) of 68.9 and a correlated color temperature (CCT) of 4340 K. The measured frequency response of the SLD revealed a -3 dB bandwidth of 560 MHz, thus demonstrating the feasibility of the device for both solid-state lighting (SSL) and visible-light communication (VLC) applications.
Collapse
|
30
|
Yonkee BP, Young EC, Lee C, Leonard JT, DenBaars SP, Speck JS, Nakamura S. Demonstration of a III-nitride edge-emitting laser diode utilizing a GaN tunnel junction contact. OPTICS EXPRESS 2016; 24:7816-7822. [PMID: 27137064 DOI: 10.1364/oe.24.007816] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate a III-nitride edge emitting laser diode (EELD) grown on a (2021) bulk GaN substrate with a GaN tunnel junction contact for hole injection. The tunnel junction was grown using a combination of metal-organic chemical-vapor deposition (MOCVD) and ammonia-based molecular-beam epitaxy (MBE) which allowed to be regrown over activated p-GaN. For a laser bar with dimensions of 1800 µm x 2.5 µm, without facet coatings, the threshold current was 284 mA (6.3 kA/cm2) and the single facet slope efficiency was 0.33 W/A (12% differential efficiency). A differential resistivity at high current density of 2.3 × 10-4 Ω cm2 was measured.
Collapse
|
31
|
Pimputkar S, Malkowski TF, Griffiths S, Espenlaub A, Suihkonen S, Speck JS, Nakamura S. Stability of materials in supercritical ammonia solutions. J Supercrit Fluids 2016. [DOI: 10.1016/j.supflu.2015.10.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
32
|
Cantore M, Pfaff N, Farrell RM, Speck JS, Nakamura S, DenBaars SP. High luminous flux from single crystal phosphor-converted laser-based white lighting system. OPTICS EXPRESS 2016; 24:A215-A221. [PMID: 26832576 DOI: 10.1364/oe.24.00a215] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The efficiency droop of light emitting diodes (LEDs) with increasing current density limits the amount of light emitted per wafer area. Since low current densities are required for high efficiency operation, many LED die are needed for high power white light illumination systems. In contrast, the carrier density of laser diodes (LDs) clamps at threshold, so the efficiency of LDs does not droop above threshold and high efficiencies can be achieved at very high current densities. The use of a high power blue GaN-based LD coupled with a single crystal Ce-doped yttrium aluminum garnet (YAG:Ce) sample was investigated for white light illumination applications. Under CW operation, a single phosphor-converted LD (pc-LD) die produced a peak luminous efficacy of 86.7 lm/W at 1.4 A and 4.24 V and a peak luminous flux of 1100 lm at 3.0 A and 4.85 V with a luminous efficacy of 75.6 lm/W. Simulations of a pc-LD confirm that the single crystal YAG:Ce sample did not experience thermal quenching at peak LD operating efficiency. These results show that a single pc-LD die is capable of emitting enough luminous flux for use in a high power white light illumination system.
Collapse
|
33
|
Lee C, Shen C, Oubei HM, Cantore M, Janjua B, Ng TK, Farrell RM, El-Desouki MM, Speck JS, Nakamura S, Ooi BS, DenBaars SP. 2 Gbit/s data transmission from an unfiltered laser-based phosphor-converted white lighting communication system. OPTICS EXPRESS 2015; 23:29779-29787. [PMID: 26698461 DOI: 10.1364/oe.23.029779] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate data transmission of unfiltered white light generated by direct modulation of a blue gallium nitride (GaN) laser diode (LD) exciting YAG:Ce phosphors. 1.1 GHz of modulation bandwidth was measured without a limitation from the slow 3.8 MHz phosphor response. A high data transmission rate of 2 Gbit/s was achieved without an optical blue-filter using a non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. The measured bit error rate (BER) of 3.50 × 10(-3) was less than the forward error correction (FEC) limit of 3.8 × 10(-3). The generated white light exhibits CIE 1931 chromaticity coordinates of (0.3628, 0.4310) with a color rendering index (CRI) of 58 and a correlated color temperature (CCT) of 4740 K when the LD was operated at 300 mA. The demonstrated laser-based lighting system can be used simultaneously for indoor broadband access and illumination applications with good color stability.
Collapse
|
34
|
Lee C, Zhang C, Cantore M, Farrell RM, Oh SH, Margalith T, Speck JS, Nakamura S, Bowers JE, DenBaars SP. 4 Gbps direct modulation of 450 nm GaN laser for high-speed visible light communication. OPTICS EXPRESS 2015; 23:16232-16237. [PMID: 26193595 DOI: 10.1364/oe.23.016232] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate high-speed data transmission with a commercial high power GaN laser diode at 450 nm. 2.6 GHz bandwidth was achieved at an injection current of 500 mA using a high-speed visible light communication setup. Record high 4 Gbps free-space data transmission rate was achieved at room temperature.
Collapse
|
35
|
Von Dollen P, Pimputkar S, Speck JS. Es werde Licht - mit Galliumnitrid: der Nobelpreis für Physik 2014. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201410693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
36
|
Von Dollen P, Pimputkar S, Speck JS. Let There Be Light-With Gallium Nitride: The 2014 Nobel Prize in Physics. Angew Chem Int Ed Engl 2014; 53:13978-80. [DOI: 10.1002/anie.201410693] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Indexed: 11/11/2022]
|
37
|
Perl EE, McMahon WE, Farrell RM, DenBaars SP, Speck JS, Bowers JE. Surface structured optical coatings with near-perfect broadband and wide-angle antireflective properties. NANO LETTERS 2014; 14:5960-5964. [PMID: 25238041 DOI: 10.1021/nl502977f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Optical thin-film coatings are typically limited to designs where the refractive index varies in only a single dimension. However, additional control over the propagation of incoming light is possible by structuring the other two dimensions. In this work, we demonstrate a three-dimensional surface structured optical coating that combines the principles of thin-film optical design with bio-inspired nanostructures to yield near-perfect antireflection. Using this hybrid approach, we attain average reflection losses of 0.2% on sapphire and 0.6% on gallium nitride for 300-1800 nm light. This performance is maintained to very wide incidence angles, achieving less than 1% reflection at all measured wavelengths out to 45° for sapphire. This hybrid design has the potential to significantly enhance the broadband and wide-angle properties for a number of optical systems that require high transparency.
Collapse
|
38
|
Hu YL, Rind E, Speck JS. Antiphase boundaries and rotation domains in In2O3(001) films grown on yttria-stabilized zirconia (001). J Appl Crystallogr 2014. [DOI: 10.1107/s1600576713033864] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In2O3is important because it has been widely used as a transparent contact material and an active gas sensor material. To understand and utilize its intrinsic physics as a semiconductor, it is necessary to have In2O3with a high material quality. In this article, single-crystalline (001)-oriented In2O3thin films were grown on yttria-stabilized zirconia (001) substrate, and a group theory analysis and transmission electron microscopy (TEM) experiments were conducted to investigate the defects within the In2O3film. Owing to the reduced symmetry of the bixbyite structure (space group Ia{\overline 3}) in comparison with the fluorite template (space group Fm {\overline 3}m), the formation of antiphase domains and 90° rotation domains in the In2O3thin films is anticipated. This prediction is confirmed experimentally by TEM and high-angle annular dark-field scanning transmission electron microscopy images. The size of the enclosed domains ranges from 50 to 300 nm, and the major domain boundaries are along the (110), (1{\overline 1}0), (010) and (100) planes. The rotation domains are related by a fourfold rotation operation along the 〈001〉 directions, which will cause the permutation of the axes of the bixbyite structure.
Collapse
|
39
|
Iveland J, Martinelli L, Peretti J, Speck JS, Weisbuch C. Direct measurement of Auger electrons emitted from a semiconductor light-emitting diode under electrical injection: identification of the dominant mechanism for efficiency droop. PHYSICAL REVIEW LETTERS 2013; 110:177406. [PMID: 23679777 DOI: 10.1103/physrevlett.110.177406] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Indexed: 06/02/2023]
Abstract
We report on the unambiguous detection of Auger electrons by electron emission spectroscopy from a cesiated InGaN/GaN light-emitting diode under electrical injection. Electron emission spectra were measured as a function of the current injected in the device. The appearance of high energy electron peaks simultaneously with an observed drop in electroluminescence efficiency shows that hot carriers are being generated in the active region (InGaN quantum wells) by an Auger process. A linear correlation was measured between the high energy emitted electron current and the "droop current"--the missing component of the injected current for light emission. We conclude that the droop phenomenon in GaN light-emitting diodes originates from the excitation of Auger processes.
Collapse
|
40
|
Feezell DF, Speck JS, DenBaars SP, Nakamura S. Semipolar $({\hbox{20}}\bar{{\hbox{2}}}\bar{{\hbox{1}}})$ InGaN/GaN Light-Emitting Diodes for High-Efficiency Solid-State Lighting. ACTA ACUST UNITED AC 2013. [DOI: 10.1109/jdt.2012.2227682] [Citation(s) in RCA: 298] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
41
|
Zhao Y, Yan Q, Feezell D, Fujito K, Van de Walle CG, Speck JS, DenBaars SP, Nakamura S. Optical polarization characteristics of semipolar (3031) and (3031) InGaN/GaN light-emitting diodes. OPTICS EXPRESS 2013; 21 Suppl 1:A53-A59. [PMID: 23389275 DOI: 10.1364/oe.21.000a53] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Linear polarized electroluminescence was investigated for semipolar (3031) and (3031) InGaN light-emitting diodes (LEDs) with various indium compositions. A high degree of optical polarization was observed for devices on both planes, ranging from 0.37 at 438 nm to 0.79 at 519 nm. The extracted valence band energy separation was consistent with the optical polarization ratios. The effect of anisotropic strain on the valance band structure was studied using k?p method for the above two planes. The theoretical calculations are consistent with the experimental results.
Collapse
|
42
|
Keller S, Dora Y, Chowdhury S, Wu F, Chen X, DenBaars SP, Speck JS, Mishra UK. Growth and characterization of N-polar GaN and AlGaN/GaN HEMTs on (111) silicon. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/pssc.201000958] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
43
|
Golan Y, Fini P, Denbaars SP, Speck JS. Substrate Surface Treatments and “Controlled Contamination” in GaN / Sapphire MOCVD. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-482-57] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractWe have used atomic force microscopy (AFM) to study the effect of common substrate surface treatments for the metal-organic chemical vapor deposition (MOCVD) of GaN on sapphire. It appears that contaminants play a major role in the surface chemistry and strongly influence the morphology of the treated surfaces. In order to investigate the role of these contaminants, we have introduced the concept of “controlled contamination” (CC), namely, exposure of the sapphire surfaces to controlled amounts of potential contaminants in-situ and investigation of the resulting sapphire morphology. The results showed that sapphire, considered to be a very stable oxide surface, is clearly reactive in the GaN MOCVD chemical environment at the high temperatures (HT) employed, allowing us to use CC for obtaining sapphire substrates with controlled roughness. Nevertheless, epitaxial growth using the two-step GaN MOCVD process appears to be very robust and practically insensitive to the (submicronscale) substrate morphology.
Collapse
|
44
|
Garrett GA, Shen H, Wraback M, Tyagi A, Schmidt MC, Speck JS, DenBaars SP, Nakamaura S. Comparison of time-resolved photoluminescence from InGaN single quantum wells grown on nonpolar and semipolar bulk GaN substrates. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/pssc.200880974] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
45
|
Reurings F, Tuomisto F, Gallinat CS, Koblmüller G, Speck JS. Vacancy defects probed with positron annihilation spectroscopy in In-polar InN grown by plasma-assisted molecular beam epitaxy: Effects of growth conditions. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/pssc.200880952] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
46
|
Schaake CA, Fichtenbaum NA, Neufeld CJ, Keller S, DenBaars SP, Speck JS, Mishra UK. M-plane InGaN/GaN light emitting diodes fabricated by MOCVD regrowth onc-plane patterned templates. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/pssc.200779284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
47
|
Choi YS, Iza M, Matioli E, Koblmüller G, Speck JS, Weisbuch C, Hu EL. Submicron-thick microcavity InGaN light emitting diodes. ACTA ACUST UNITED AC 2008. [DOI: 10.1117/12.764696] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
|
48
|
Hashimoto T, Wu F, Speck JS, Nakamura S. A GaN bulk crystal with improved structural quality grown by the ammonothermal method. NATURE MATERIALS 2007; 6:568-71. [PMID: 17603489 DOI: 10.1038/nmat1955] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Accepted: 06/01/2007] [Indexed: 05/16/2023]
Abstract
The realization of high-performance optoelectronic devices, based on GaN and other nitride semiconductors, requires the existence of a high-quality substrate. Non-polar or semipolar substrates have recently been proven to provide superior optical devices to those on conventional c-plane substrates. Bulk GaN growth enables GaN substrates sliced along various favourable crystal orientations. Ammonothermal growth is an attractive method for bulk GaN growth owing to its potential to grow GaN ingots at low cost. Here we report on improvement in the structural quality of GaN grown by the ammonothermal method. The threading dislocation densities estimated by plan-view transmission electron microscopy observations were less than 1 x 10(6) cm(-2) for the Ga face and 1 x 10(7) cm(-2) for the N face. No dislocation generation at the interface was observed on the Ga face, although a few defects were generated at the interface on the N face. The improvement in the structural quality, together with the previous report on growth rate and scalability, demonstrates the commercial feasibility of the ammonothermal GaN growth.
Collapse
|
49
|
Fehlberg TB, Umana-Membreno GA, Gallinat CS, Koblmüller G, Bernardis S, Nener BD, Parish G, Speck JS. Characterisation of multiple carrier transport in indium nitride grown by molecular beam epitaxy. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/pssc.200674780] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
50
|
Chichibu SF, Uedono A, Onuma T, Haskell BA, Chakraborty A, Koyama T, Fini PT, Keller S, Denbaars SP, Speck JS, Mishra UK, Nakamura S, Yamaguchi S, Kamiyama S, Amano H, Akasaki I, Han J, Sota T. Origin of defect-insensitive emission probability in In-containing (Al,In,Ga)N alloy semiconductors. NATURE MATERIALS 2006; 5:810-6. [PMID: 16951678 DOI: 10.1038/nmat1726] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 07/12/2006] [Indexed: 05/11/2023]
Abstract
Group-III-nitride semiconductors have shown enormous potential as light sources for full-colour displays, optical storage and solid-state lighting. Remarkably, InGaN blue- and green-light-emitting diodes (LEDs) emit brilliant light although the threading dislocation density generated due to lattice mismatch is six orders of magnitude higher than that in conventional LEDs. Here we explain why In-containing (Al,In,Ga)N bulk films exhibit a defect-insensitive emission probability. From the extremely short positron diffusion lengths (<4 nm) and short radiative lifetimes of excitonic emissions, we conclude that localizing valence states associated with atomic condensates of In-N preferentially capture holes, which have a positive charge similar to positrons. The holes form localized excitons to emit the light, although some of the excitons recombine at non-radiative centres. The enterprising use of atomically inhomogeneous crystals is proposed for future innovation in light emitters even when using defective crystals.
Collapse
|