Current crowding effect on the ideality factor and efficiency droop in blue lateral InGaN/GaN light emitting diodes

Abstract

By examining two types of lateral InGaN/GaN light emitting diodes with different contact patterns, we demonstrate that in the intermediate range of current where the space-charge region dominates in the device performance, the ideality factor (β) increases from 1.9 (current spreading design) up to 2.4 (current crowding design). This modification of β-factor could be erroneously treated as the change of free carrier recombination nature. The current crowding design is also responsible for the local overheating and heavier efficiency droop that occurs at the characteristic current 2.3 times smaller in comparison with the current spreading design.

InGaN micro-LED-pillar as the building block for high brightness emitters

“…Thus a uniform current spreading (larger fraction) in smaller µLED-pillar results in the improved electrical property. Furthermore, with a reduced size, the current crowding effect at the active region is less significant, leading to reduced Auger recombination probability, and local heating [9].…”

Mesa-height Dependent Quantum Efficiency Characteristics of InGaN Micro-LEDs

“…Growing on insulating sapphire substrate, InGaN/GaN LED epitaxy also suffers from the effect of non-uniform current distribution, or the current crowding effect, resulting in an exacerbated efficiency droop [5]. The current spreading in an InGaN/GaN micro-LED is illustrated in Fig.…”

“…Micro-LEDs show improved efficiency at high injection current density although the efficiency was affected via side-wall defects induced non-radiative recombination at low injection [4]. The high efficiency at high injection was attributed to enhanced current spreading in micro-LEDs, which resulted in a reduction of efficiency droop effect [5]. Other potential advantages of micro-LED include enhanced light extraction [6] and suitability in optoelectronic integration [7].…”

Reduction of Current Crowding in InGaN-based Blue Light-Emitting Diodes by Modifying Metal Contact Geometry

“…Over the past years, there have been many researches to analyze and improve the efficiency droop of the LEDs [1][2][3][4][5][6][7][8]. It is known that current crowding is one of the major obstacles to solving the droop problem and increasing internal quantum efficiency [9,10]. In addition, current crowding is also related with the negative-voltage electrostatic discharge (ESD) problem of the LEDs [11].…”