Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes

Sadaf, Sharif Md.; Ra, Yong–Ho; Szkopek, Thomas; Mi, Zetian

doi:10.1021/acs.nanolett.5b04215

Cited by 55 publications

(27 citation statements)

References 46 publications

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“…We have performed extensive studies of the nonpolar core–shell UV LED by comparing a uniaxial AlGaN nanowire UV LED which has vertical MQW heterostructures grown along a <0001> polar direction of n‐GaN nanowire. The detailed characterization of the uniaxial nanowire LED structures was described elsewhere . The core–shell UV‐LED device ( 318 nm wavelength) showed significantly smaller turn‐on voltage and reduced resistance compared to that of the uniaxial nanowire UV LED (322 nm wavelength), shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

Ultraviolet Light‐Emitting Diode Using Nonpolar AlGaN Core–Shell Nanowire Heterostructures

Kang

Lee

2018

Advanced Optical Materials

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To date, semiconductor light emitters have been developed to exceed 50% efficiency across the entire visible region. [6,7] However, the performance of AlGaNbased ultraviolet light-emitting diodes (LEDs) has been severely limited by the extremely inefficient strain-induced polarization fields and prohibitively large defect densities. Various approaches, including sputtered AlN nucleation layer, polarization doping, patterned sapphire substrate (PSS), AlGaN superlattices, and non-/ semipolars have been studied to improve the efficiency of LEDs in the ultraviolet region. [1,[8][9][10][11][12] Due to low magnesium (Mg)doping efficiency and large Mg activation energy, [13][14][15] AlGaN-based LEDs usually exhibit very high threshold voltages in the deep ultraviolet range. [13,16] Furthermore, the lattice mismatch between AlGaN materials and the substrate materials induces high dislocations and stacking faults with thermal stress in the Al-rich AlGaN epitaxial layers. [14] The AlGaN multiple quantum wells (MQWs) grown along a polar [0001] orientation suffer from inherent spontaneous and piezoelectric polarizations. The total polarization fields result in the spatial separation of the electron and hole wave functions and thus in restricting the radiative recombination efficiency, known as the quantum-confined Stark effect (QCSE). [17,18] As a result, because of the poor material quality and the polarization-induced electric field, it is still difficult to achieve internal quantum efficiency (IQE) in AlGaN epitaxial structures. This poor internal quantum efficiency eventually leads to extremely low output power of AlGaN-based LEDs operating in the UVA-C bands.Such critical issues can be potentially addressed by employing 1D nanowire structures and nonpolar core-shell heterostructures. [1,12] GaN-based nanowire structures have been intensively studied in the past decade. [19][20][21] Recent reports have shown that such nanowires can drastically reduce the dislocation densities due to efficient surface strain relaxation, and also can significantly enhance the p-type current conduction due to reduced Mg-dopant formation energy in p-Al(Ga)N structures. [22,23] With the use of nonpolar structures grown along m-plane direction in GaN structure, the improved light output power and electrical performance have been demonstrated in InGaN-based quantum well LEDs with the absence of polarization. [12,24,25] Therefore, it is expected that the incorporation of the nonpolar core-shell and the nanowire structures can significantly improve the internal quantum efficiency, p-contact Highly efficient nonpolar AlGaN nanowire ultraviolet light-emitting diode is developed, wherein core-shell AlGaN multiple quantum well layers are incorporated in the nonpolar active regions. It is confirmed that the core-shell light-emitting diode (LED) heterostructures are uniformly grown on the nonpolar surfaces of hexagonal GaN nanowires by metalorganic chemical vapor deposition (MOCVD) technique. At room temperature, the nearly defect-free core-shell AlGaN...

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Section: Resultsmentioning

confidence: 99%

Ultraviolet Light‐Emitting Diode Using Nonpolar AlGaN Core–Shell Nanowire Heterostructures

Kang

Lee

2018

Advanced Optical Materials

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“…The huge opportunity in consumer electronics and the increasing applications in virtual reality, wearable devices, augmented reality, and medical applications become the major driving force behind the recent rapidly growing development in miniand micro-LEDs (Park et al, 2009;Scharf et al, 2016;Son et al, 2018;Roche, 2019;Tang et al, 2019;Zhang et al, 2020). Extensive efforts of research have been devoted to studying the influence of size-reduction in the GaN-based LEDs (Choi et al, 2003a;Sadaf et al, 2016;Kang et al, 2017;Wu et al, 2018;Huang et al, 2019;Wong et al, 2019;Lin and Jiang, 2020). Francois et al reported the lower external quantum efficiency (EQE) and maximum EQE when the LED devices went smaller (Olivier et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Experimental and Modeling Investigations of Miniaturization in InGaN/GaN Light-Emitting Diodes and Performance Enhancement by Micro-Wall Architecture

Zhang

Qiu³

et al. 2021

Front. Chem.

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The recent technological trends toward miniaturization in lighting and display devices are accelerating the requirement for high-performance and small-scale GaN-based light-emitting diodes (LEDs). In this work, the effect of mesa size-reduction in the InGaN/GaN LEDs is systematically investigated in two lateral dimensions (x- and y-directions: parallel to and perpendicular to the line where p-n directions are) both experimentally and numerically. The role of the lateral size-reduction in the x- and y-directions in improving LED performance is separately identified through experimental and modeling investigations. The narrowed dimension in the x-direction is found to cause and dominate the alleviated current crowding phenomenon, while the size-reduction in the y-direction has a minor influence on that. The size-reduction in the y-orientation induces an increased ratio of perimeter-to-area in miniaturized LED devices, which leads to improved thermal dissipation and light extraction through the sidewalls. The grown and fabricated LED devices with varied dimensions further support this explanation. Then the effect of size-reduction on the LED performance is summarized. Moreover, three-micro-walls LED architecture is proposed and demonstrated to further promote light extraction and reduce the generation of the Joule heat. The findings in this work provide instructive guidelines and insights on device miniaturization, especially for micro-LED devices.

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“…GaN-based light-emitting diodes (LEDs) have attracted widespread concern for automotive front lighting, solid-state lighting, urban landscape lighting, backlights for liquid crystal displays (LCDs), visible light communications, and so forth [1,2,3,4,5,6,7,8,9]. Currently, it is significantly crucial to drive LEDs at high current densities for the demand of high-power LED.…”

Section: Introductionmentioning

confidence: 99%

High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

et al. 2019

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We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off (LLO) process. The silicon substrate with high thermal conductivity can provide a satisfactory path for heat dissipation of VLEDs. The nitrogen polar n-GaN surface was textured by KOH solution, which not only improved light extract efficiency (LEE) but also broke down Fabry–Pérot interference in VLEDs. As a result, a near Lambertian emission pattern was obtained in a VLED. To improve current spreading, the ring-shaped n-electrode was uniformly distributed over the entire VLED. Our combined numerical and experimental results revealed that the VLED exhibited superior heat dissipation and current spreading performance over a flip-chip LED (FCLED). As a result, under 350 mA injection current, the forward voltage of the VLED was 0.36 V lower than that of the FCLED, while the light output power (LOP) of the VLED was 3.7% higher than that of the FCLED. The LOP of the FCLED saturated at 1280 mA, but the light output saturation did not appear in the VLED.

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Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes

Cited by 55 publications

References 46 publications

Ultraviolet Light‐Emitting Diode Using Nonpolar AlGaN Core–Shell Nanowire Heterostructures

Ultraviolet Light‐Emitting Diode Using Nonpolar AlGaN Core–Shell Nanowire Heterostructures

Experimental and Modeling Investigations of Miniaturization in InGaN/GaN Light-Emitting Diodes and Performance Enhancement by Micro-Wall Architecture

High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

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