Artificially formed resistive ITO/p-GaN junction to suppress the current spreading and decrease the surface recombination for GaN-based micro-light emitting diodes

Abstract

Due to the increased surface-to-volume ratio, the surface recombination caused by sidewall defects is a key obstacle that limits the external quantum efficiency (EQE) for GaN-based micro-light-emitting diodes (µLEDs). In this work, we propose selectively removing the periphery p+-GaN layer so that the an artificially formed resistive ITO/p-GaN junction can be formed at the mesa edge. Three types of LEDs with different device dimensions of 30 × 30 µm2, 60 × 60 µm2 and 100 × 100 µm2 are investigated, respectively. We find that such resistive ITO/p-GaN junction can effectively prevent the holes from reaching the sidewalls for µLEDs with smaller size. Furthermore, such confinement of injection current also facilitates the hole injection into the active region for µLEDs. Therefore, the surface-defect-caused nonradiative recombination in the edge of mesa can be suppressed. Meantime, a reduction of current leakage caused by the sidewall defects can also be obtained. As a result, the measured and calculated external quantum efficiency (EQE) and optical output power for the proposed LED with small sizes are increased.

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

“…On the one hand, research [3,[18][19][20]36] focuses on the top contact shapes that ensure a more uniform current spread. On the other hand, studies concentrate on reducing the current crowding effect by improving the geometry [11,17] or properties [15,21] of transparent conductive layers. In [36,37], additional graphene interlayers are considered to improve lateral current flow for better distribution, while entering the active region.…”

“…It causes intensive investigation of their design, technology, and features, carried out by both by industry and university research teams. The studies focus on different design concepts such as vertical [1][2][3], lateral [4,5] or 3D core-shell [6][7][8][9] devices, discussing their fabrication technologies [10][11][12], or aiming at their features employing experimental [13,14] or numerical [15][16][17] approaches.…”

Comprehensive Investigation of Electrical and Optical Characteristics of InGaN-Based Flip-Chip Micro-Light-Emitting Diodes

“…In general, R Auger is more significant at the high current densities, while R SRH is dominant at the low current densities (thus, under general operating conditions of micro-LED devices). In view of the high perimeter-to-area ratios of micro-LEDs, the trap-assisted surface non-radiative recombination occurring at mesa surfaces was also considered [ 3 ], setting the trap levels 0.46 eV above the valence band and 0.24 eV below the conduction band [ 25 ], and setting the surface recombination velocities (SRVs) for both electrons and holes ( v s,n and v s,p , respectively) around 1000 cm/s ( Table 1 ) [ 13 ]. Through electrical simulation under different biases, the spatial distributions of carrier concentrations, current flows, various recombination rates, and spontaneous emission rates as a function of bias, J–V characteristics, and electroluminescence (EL) and IQE as a function of bias can be analyzed.…”

AlGaN multiple quantum well deep‐ultraviolet micro‐light‐emitting diodes for high color conversion efficiency quantum dots display

“…Displays based on inorganic micro-light-emitting diodes (micro-LEDs) are considered one of the most promising display technologies for the next generation. [1][2][3][4][5][6] While the traditional R/G/B display technology requires three different active regions to address different colors on the same chip, [7][8][9] the quantum dot (QD)-based micro-LED display becomes an accessible solution. Blue micro-LEDs as the pumping source with red and green QDs were widely researched, and the low efficiency for pumping green QDs and the color mixing became the main problem.…”

“…Displays based on inorganic micro‐light‐emitting diodes (micro‐LEDs) are considered one of the most promising display technologies for the next generation 1–6 . While the traditional R/G/B display technology requires three different active regions to address different colors on the same chip, 7–9 the quantum dot (QD)‐based micro‐LED display becomes an accessible solution.…”