Theoretical considerations on efficiency degradation due to thermal effect in a planar GaN-based LED with a GaN substrate

Abstract

In this paper, using a fully-coupled, three-dimensional electro-thermal device simulator, we study the mechanism of efficiency degradation at high current operation in planar GaN-based light emitting diodes (LED). In particular, the improvement of the efficiency degradation using thicker conductive GaN substrates has been demonstrated. First, it is found that local Joule heating inside thin conductive GaN substrates degrades internal quantum efficiency (IQE) and increases the series resistance. Then, we introduced thicker conductive GaN substrates and simulated distributions of the current density and temperature inside the substrate. It is found that the maximum current density inside the GaN substrate decreases by about six times for a 100-µm-thick substrate compared to that for a 5-µm-thick substrate. Therefore, the maximum junction temperature decreases, and then IQE and the driving voltage are improved. The present study proves that thick GaN substrates are effective to improve the properties of planar LEDs at high current operation.

Thermal Effects on the Electrical and Optical Characteristics of Micro‐Light‐Emitting Diodes with Different Current Spreading Layer

“…Consequently, the higher ambient temperature could induce a lower equivalent resistance, and thus lower forward voltage and internal heat source density. In addition, the increased temperature reduces the internal quantum efficiency (IQE) by increasing the nonradiative combination and carrier leakage, and thus the LOP decreases. For the EQE, its temperature dependence generally follows the trend of the LOP, except that bulges appear at low injected current densities in Figure (c) and 5(c).…”

“…In addition, in some applications, such as the VLC between automobiles through headlights, the micro‐LED may operate under an increased ambient temperature, which can be as high as 90 °C . Therefore, the thermal effects on the electrical and optical performances are important issues …”

Analysis of Current Transport Layer Localized Resistivity Increase After High Stress on InGaN LEDs

“…9. The model is based on the analysis carried out by Sato-Iwanaga et al [9]. Since we are focusing on the instantaneous effect during a pulsed measurement, the temperature is neglected in the simplified model reported in Fig.…”

“…[10], [9], [11], those areas suffer a reduction in their electrical conductivity, thus, as the local series resistance increases, the current flows through the next closer low resistance path. This path, previously biased by a lower current, now contributes in spreading the current over a bigger area, thus reducing the current crowding and increasing the radiative efficiency [4], [12].…”

Mechanism of GaN CMP Based on H2O2Slurry Combined with UV Light

“…Within the upstream industry, the substrate material is the most important factor that determines the color, brightness, life-time, and other performance indexes of LEDs. [1][2][3][4] Certain criteria for substrate selection should be considered, such as similar crystal structure and composition, lattice matching, thermal expansion coefficient matching, high chemical stability, large size, easily integration and heat dissipation. 5 At present, only two kinds of substrates are used commercially, sapphire and silicon carbide (SiC), while other substrates are still being investigated.…”