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Wang Y, Zhang Z, Guo L, Chen Y, Li Y, Qi Z, Ben J, Sun X, Li D. Calculating the Effect of AlGaN Dielectric Layers in a Polarization Tunnel Junction on the Performance of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes. NANOMATERIALS 2021; 11:nano11123328. [PMID: 34947677 PMCID: PMC8707888 DOI: 10.3390/nano11123328] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/28/2021] [Accepted: 12/02/2021] [Indexed: 11/24/2022]
Abstract
In this work, AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) with AlGaN as the dielectric layers in p+-Al0.55Ga0.45N/AlGaN/n+-Al0.55Ga0.45N polarization tunnel junctions (PTJs) were modeled to promote carrier tunneling, suppress current crowding, avoid optical absorption, and further enhance the performance of LEDs. AlGaN with different Al contents in PTJs were optimized by APSYS software to investigate the effect of a polarization-induced electric field (Ep) on hole tunneling in the PTJ. The results indicated that Al0.7Ga0.3N as a dielectric layer can realize a higher hole concentration and a higher radiative recombination rate in Multiple Quantum Wells (MQWs) than Al0.4Ga0.6N as the dielectric layer. In addition, Al0.7Ga0.3N as the dielectric layer has relatively high resistance, which can increase lateral current spreading and enhance the uniformity of the top emitting light of LEDs. However, the relatively high resistance of Al0.7Ga0.3N as the dielectric layer resulted in an increase in the forward voltage, so much higher biased voltage was required to enhance the hole tunneling efficiency of PTJ. Through the adoption of PTJs with Al0.7Ga0.3N as the dielectric layers, enhanced internal quantum efficiency (IQE) and optical output power will be possible.
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Affiliation(s)
- Yong Wang
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
- State Key Laboratory of High Power Semiconductor Lasers, Chang Chun University of Science and Technology, Changchun 130022, China
| | - Zihui Zhang
- Key Laboratory of Electronic Materials and Devices of Tianjin, School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401, China;
- Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300401, China
| | - Long Guo
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuxuan Chen
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yahui Li
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhanbin Qi
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jianwei Ben
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaojuan Sun
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dabing Li
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (Y.W.); (L.G.); (Y.C.); (Y.L.); (Z.Q.); (J.B.); (X.S.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
- Correspondence:
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Gibasiewicz K, Bojarska-Cieślińska A, Muzioł G, Skierbiszewski C, Grzanka S, Kafar A, Perlin P, Najda S, Suski T. InGaN blue light emitting micro-diodes with current path defined by tunnel junction. OPTICS LETTERS 2020; 45:4332-4335. [PMID: 32735291 DOI: 10.1364/ol.394629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
We have fabricated tunnel-junction InGaN micro-LEDs using plasma-assisted molecular beam epitaxy technology, with top-down processing on GaN substrates. Devices have diameters between 5 µm and 100 µm. All of the devices emit light at 450 nm at a driving current density of about 10Acm-2. We demonstrate that within micro-LEDs ranging in size from 100 µm down to 5 µm, the properties of these devices, both electrical and optical, are fully scalable. That means we can reproduce all electro-optical characteristics using a single set of parameters. Most notably, we do not observe any enhancement of non-radiative recombination for the smallest devices. We assign this result to a modification of the fabrication process, i.e., replacement of deep dry etching by a tunnel junction for the current confinement. These devices show excellent thermal stability of their light emission characteristics, enabling operation at current densities up to 1kAcm-2.
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Shin W, Pandey A, Liu X, Sun Y, Mi Z. Photonic crystal tunnel junction deep ultraviolet light emitting diodes with enhanced light extraction efficiency. OPTICS EXPRESS 2019; 27:38413-38420. [PMID: 31878609 DOI: 10.1364/oe.380739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 12/05/2019] [Indexed: 06/10/2023]
Abstract
We report on the demonstration of top emitting AlGaN tunnel junction deep ultraviolet (UV) light emitting didoes (LEDs) operating at ∼267 nm. We show, both theoretically and experimentally, that the light extraction efficiency can be enhanced by nearly a factor of two with the incorporation of AlGaN nanowire photonic crystal structures. A peak wall-plug efficiency (WPE) ∼3.5% and external quantum efficiency (EQE) ∼5.4% were measured for AlGaN LEDs directly on-wafer without any packaging. This work demonstrates a viable path for achieving high efficiency deep UV LEDs through the integration of AlGaN planar and nanoscale structures.
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Growden TA, Zhang W, Brown ER, Storm DF, Meyer DJ, Berger PR. Near-UV electroluminescence in unipolar-doped, bipolar-tunneling GaN/AlN heterostructures. LIGHT, SCIENCE & APPLICATIONS 2018; 7:17150. [PMID: 30839526 PMCID: PMC6060061 DOI: 10.1038/lsa.2017.150] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Revised: 10/05/2017] [Accepted: 10/23/2017] [Indexed: 06/09/2023]
Abstract
Cross-gap light emission is reported in n-type unipolar GaN/AlN double-barrier heterostructure diodes at room temperature. Three different designs were grown on semi-insulating bulk GaN substrates using molecular beam epitaxy (MBE). All samples displayed a single electroluminescent spectral peak at 360 nm with full-width at half-maximum (FWHM) values no greater than 16 nm and an external quantum efficiency (EQE) of ≈0.0074% at 18.8 mA. In contrast to traditional GaN light emitters, p-type doping and p-contacts are completely avoided, and instead, holes are created in the GaN on the emitter side of the tunneling structure by direct interband (that is, Zener) tunneling from the valence band to the conduction band on the collector side. The Zener tunneling is enhanced by the high electric fields (~5 × 106 V cm-1) created by the notably large polarization-induced sheet charge at the interfaces between the AlN and GaN.
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Affiliation(s)
- Tyler A Growden
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA
| | - Weidong Zhang
- Departments of Physics and Electrical Engineering, Wright State University, Dayton, Ohio 45435, USA
| | - Elliott R Brown
- Departments of Physics and Electrical Engineering, Wright State University, Dayton, Ohio 45435, USA
| | - David F Storm
- US Naval Research Laboratory, Washington, DC 20375, USA
| | - David J Meyer
- US Naval Research Laboratory, Washington, DC 20375, USA
| | - Paul R Berger
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA
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Saha PK, Chouksey S, Ganguly S, Saha D. Temperature-independent optical transition with sub-nanometer linewidth in thermally diffused Gadolinium in GaN. OPTICS LETTERS 2017; 42:2161-2164. [PMID: 28569871 DOI: 10.1364/ol.42.002161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/08/2017] [Indexed: 06/07/2023]
Abstract
We have demonstrated temperature-independent optical transitions from thermally diffused Gd in GaN. The emission wavelength is sub-bandgap with respect to GaN. The origin of photon generation is identified as atomic transitions in Gd hosted in the weak interaction field of GaN. The emission linewidth remains sub-nanometer (0.1-0.6 nm) from 19 to 300 K for all the optical pumping intensities. The shift in wavelength with temperature and optical pumping is negligible (∼0.8 nm) for the entire temperature window. The output intensity is found to scale linearly with the pumping power. The magnetic, electrical, and physical characterizations indicate that Gd acts as an electron trap in GaN. Transient absorption spectroscopy discovers a major nonradiative parallel path for carrier leaking. The observed characteristics may find potential applications in narrow linewidth optical sources.
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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.
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Sadaf SM, Ra YH, Szkopek T, Mi Z. Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes. NANO LETTERS 2016; 16:1076-1080. [PMID: 26812264 DOI: 10.1021/acs.nanolett.5b04215] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We have demonstrated for the first time an n(++)-GaN/Al/p(++)-GaN backward diode, wherein an epitaxial Al layer serves as the tunnel junction. The resulting p-contact free InGaN/GaN nanowire light-emitting diodes (LEDs) exhibited a low turn-on voltage (∼2.9 V), reduced resistance, and enhanced power, compared to nanowire LEDs without the use of Al tunnel junction or with the incorporation of an n(++)-GaN/p(++)-GaN tunnel junction. This unique Al tunnel junction overcomes some of the critical issues related to conventional GaN-based tunnel junction designs, including stress relaxation, wide depletion region, and light absorption, and holds tremendous promise for realizing low-resistivity, high-brightness III-nitride nanowire LEDs in the visible and deep ultraviolet spectral range. Moreover, the demonstration of monolithic integration of metal and semiconductor nanowire heterojunctions provides a seamless platform for realizing a broad range of multifunctional nanoscale electronic and photonic devices.
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Affiliation(s)
- S M Sadaf
- Department of Electrical and Computer Engineering, McGill University 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - Y H Ra
- Department of Electrical and Computer Engineering, McGill University 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - T Szkopek
- Department of Electrical and Computer Engineering, McGill University 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - Z Mi
- Department of Electrical and Computer Engineering, McGill University 3480 University Street, Montreal, Quebec H3A 0E9, Canada
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Sadaf SM, Ra YH, Nguyen HPT, Djavid M, Mi Z. Alternating-Current InGaN/GaN Tunnel Junction Nanowire White-Light Emitting Diodes. NANO LETTERS 2015; 15:6696-701. [PMID: 26384135 DOI: 10.1021/acs.nanolett.5b02515] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The current LED lighting technology relies on the use of a driver to convert alternating current (AC) to low-voltage direct current (DC) power, a resistive p-GaN contact layer to inject positive charge carriers (holes) for blue light emission, and rare-earth doped phosphors to down-convert blue photons into green/red light, which have been identified as some of the major factors limiting the device efficiency, light quality, and cost. Here, we show that multiple-active region phosphor-free InGaN nanowire white LEDs connected through a polarization engineered tunnel junction can fundamentally address the afore-described challenges. Such a p-GaN contact-free LED offers the benefit of carrier regeneration, leading to enhanced light intensity and reduced efficiency droop. Moreover, through the monolithic integration of p-GaN up and p-GaN down nanowire LED structures on the same substrate, we have demonstrated, for the first time, AC operated LEDs on a Si platform, which can operate efficiently in both polarities (positive and negative) of applied voltage.
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Affiliation(s)
- S M Sadaf
- Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - Y-H Ra
- Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - H P T Nguyen
- Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - M Djavid
- Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada
| | - Z Mi
- Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada
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Zhang K, Liang H, Liu Y, Shen R, Guo W, Wang D, Xia X, Tao P, Yang C, Luo Y, Du G. Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction grown by metal-organic chemical vapor deposition on sapphire substrate. Sci Rep 2014; 4:6322. [PMID: 25205042 PMCID: PMC4159626 DOI: 10.1038/srep06322] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 08/19/2014] [Indexed: 11/09/2022] Open
Abstract
Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction (PIBTJ) was grown by metal-organic chemical vapor deposition on sapphire substrate. A self-consistent solution of Poisson-Schrödinger equations combined with polarization-induced theory was used to model PIBTJ structure, energy band diagrams and free carrier concentrations distribution. The PIBTJ displays reliable and reproducible backward tunneling with a current density of 3 A/cm2 at the reverse bias of −1 V. The absence of negative differential resistance behavior of PIBTJ at forward bias can mainly be attributed to the hole compensation centers, including C, H and O impurities, accumulated at the p-GaN/Mg-doped AlGaN heterointerface.
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Affiliation(s)
- Kexiong Zhang
- 1] School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China [2]
| | - Hongwei Liang
- 1] School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China [2]
| | - Yang Liu
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Rensheng Shen
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Wenping Guo
- Jiangsu Xinguanglian Technology Co., Ltd., Wuxi 214192, China
| | - Dongsheng Wang
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Xiaochuan Xia
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Pengcheng Tao
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Chao Yang
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Yingmin Luo
- School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China
| | - Guotong Du
- 1] School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024, China [2] State Key Laboratory on Integrated Optoelectronics, School of Electronic Science and Engineering, Jilin University, Changchun 130012, China
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Carnevale SD, Kent TF, Phillips PJ, Sarwar ATMG, Selcu C, Klie RF, Myers RC. Mixed polarity in polarization-induced p-n junction nanowire light-emitting diodes. NANO LETTERS 2013; 13:3029-3035. [PMID: 23756087 DOI: 10.1021/nl400200g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Polarization-induced nanowire light emitting diodes (PINLEDs) are fabricated by grading the Al composition along the c-direction of AlGaN nanowires grown on Si substrates by plasma-assisted molecular beam epitaxy (PAMBE). Polarization-induced charge develops with a sign that depends on the direction of the Al composition gradient with respect to the [0001] direction. By grading from GaN to AlN then back to GaN, a polarization-induced p-n junction is formed. The orientation of the p-type and n-type sections depends on the material polarity of the nanowire (i.e., Ga-face or N-face). Ga-face material results in an n-type base and a p-type top, while N-face results in the opposite. The present work examines the polarity of catalyst-free nanowires using multiple methods: scanning transmission electron microscopy (STEM), selective etching, conductive atomic force microscopy (C-AFM), and electroluminescence (EL) spectroscopy. Selective etching and STEM measurements taken in annular bright field (ABF) mode demonstrate that the preferred orientation for catalyst-free nanowires grown by PAMBE is N-face, with roughly 10% showing Ga-face orientation. C-AFM and EL spectroscopy allow electrical and optical differentiation of the material polarity in PINLEDs since the forward bias direction depends on the p-n junction orientation and therefore on nanowire polarity. Specifically, C-AFM reveals that the direction of forward bias for individual nanowire LEDs changes with the polarity, as expected, due to reversal of the sign of the polarization-induced charge. Electroluminescence measurements of mixed polarity PINLEDs wired in parallel show ambipolar emission due to the mixture of p-n and n-p oriented PINLEDs. These results show that, if catalyst-free III-nitride nanowires are to be used to form polarization-doped heterostructures, then it is imperative to understand their mixed polarity and to design devices using these nanowires accordingly.
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Affiliation(s)
- Santino D Carnevale
- Department of Materials Science and Engineering, ‡Department of Electrical and Computer Engineering, and §Department of Physics, Ohio State University, Columbus, Ohio 43210, United States
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Krishnamoorthy S, Kent TF, Yang J, Park PS, Myers RC, Rajan S. GdN nanoisland-based GaN tunnel junctions. NANO LETTERS 2013; 13:2570-2575. [PMID: 23662669 DOI: 10.1021/nl4006723] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Tunnel junctions could have a great impact on gallium nitride and aluminum nitride-based devices such as light-emitting diodes and lasers by overcoming critical challenges related to hole injection and p-contacts. This paper demonstrates the use of GdN nanoislands to enhance interband tunneling and hole injection into GaN p-n junctions by several orders of magnitude, resulting in low tunnel junction specific resistivity (1.3 × 10(-3) Ω-cm(2)) compared to the previous results in wide band gap semiconductors. Tunnel injection of holes was confirmed by low-temperature operation of GaN p-n junction with a tunneling contact layer, and strong electroluminescence down to 20 K. The low tunnel junction resistance combined with low optical absorption loss in GdN is very promising for incorporation in GaN-based light emitters.
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Affiliation(s)
- Sriram Krishnamoorthy
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA
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Carnevale SD, Kent TF, Phillips PJ, Mills MJ, Rajan S, Myers RC. Polarization-induced pn diodes in wide-band-gap nanowires with ultraviolet electroluminescence. NANO LETTERS 2012; 12:915-920. [PMID: 22268600 DOI: 10.1021/nl203982p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors.
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Affiliation(s)
- Santino D Carnevale
- Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA
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Simon J, Zhang Z, Goodman K, Xing H, Kosel T, Fay P, Jena D. Polarization-induced Zener tunnel junctions in wide-band-gap heterostructures. PHYSICAL REVIEW LETTERS 2009; 103:026801. [PMID: 19659229 DOI: 10.1103/physrevlett.103.026801] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Indexed: 05/28/2023]
Abstract
The large electronic polarization in III-V nitrides allows for novel physics not possible in other semiconductor families. In this work, interband Zener tunneling in wide-band-gap GaN heterojunctions is demonstrated by using polarization-induced electric fields. The resulting tunnel diodes are more conductive under reverse bias, which has applications for zero-bias rectification and mm-wave imaging. Since interband tunneling is traditionally prohibitive in wide-band-gap semiconductors, these polarization-induced structures and their variants can enable a number of devices such as multijunction solar cells that can operate under elevated temperatures and high fields.
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Affiliation(s)
- John Simon
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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Mirhosseini R, Schubert MF, Chhajed S, Cho J, Kim JK, Schubert EF. Improved color rendering and luminous efficacy in phosphor-converted white light-emitting diodes by use of dual-blue emitting active regions. OPTICS EXPRESS 2009; 17:10806-10813. [PMID: 19550480 DOI: 10.1364/oe.17.010806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Conventional white-light sources suffer from a fundamental trade-off between color rendering index and the luminous efficacy; increasing one generally comes at the expense of the other. We demonstrate through simulation that dual-wavelength blue-emitting active regions in phosphor-converted white light sources maximize the output luminous flux while significantly increasing the color rendering ability. Our results indicate that such improvements can be achieved over a broad range of correlated color temperatures.
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Affiliation(s)
- Roya Mirhosseini
- Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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