Efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes with nonuniform current spreading

Abstract

We demonstrate that the efficiency droop phenomenon in multiple quantum well InGaN/GaN light-emitting diodes (LEDs) may be connected to the current crowding effect. A numerical model of internal quantum efficiency calculation is presented that takes into account nonuniform lateral carrier injection in the active region. Based on this model, we examine the effect of current crowding on the efficiency droop using comparison of simulated internal quantum efficiency of InGaN LEDs with low and high uniformity of current spreading. The results of simulations and measurements show that the devices with low uniformity of current spreading exhibit higher efficiency droop and lower roll-off current value.

Correlating electroluminescence characterization and physics-based models of InGaN/GaN LEDs: Pitfalls and open issues

“…Refs. [35][36][37][38][39][40][41]. The simulated lateral profile of the vertical component of the electron current density J n, y (x) in the present devices at a current I = 100 mA (J = 40 A/cm 2 ) is reported in Fig.…”

“…Since the n-side metallization surrounds the entire mesa periphery, in the presence of current crowding a fully 3D simulation should be required. 7,38,[50][51][52][53][54][55] Thanks to the device symmetries and lateral dimensions, in the following Sections a quasi-3D approximation has been adopted by determining temperature-dependent correction factors f J,ring (T ; V ) = J 3D (T ; V )/J 2D (T ; V ) and f L ,ring (T ; V ) = L 3D (T ; V )/L 2D (T ; V ), used to weight the 2D-simulated current density and emitted optical power when compared with the corresponding experimental values. This approximation has been validated against fully-3D simulations performed with TCAD SENTAURUS on increasingly realistic test structures (see Figs.…”

Nanorods on surface of GaN-based thin-film LEDs deposited by post-annealing after photo-assisted chemical etching

“…The aims of the experimental stage are high reliability and low equipment cost. However, with the evolution of metal electrode materials and constant improvement in relevant processes, flip-chip LED technology has matured into something quite different from traditional LED technology [6–10]. Recently, thin film LEDs have attracted considerable attention as components in light sources for portable electronic devices because they are flat.…”

Performance enhancement of blue light-emitting diodes by using special designed n and p-type doped barriers

“…However, the haunting efficiency droop at high injection levels is still a large obstacle for InGaN/GaN LEDs to be competitive in terms of its high-brightness and high-power applications [3,4]. According to the literatures, people have proposed some possible physical mechanisms for efficiency droop such as the Auger recombination [5], poor hole injection efficiency [6], electron leakage [7], polarization effect [8], current crowding effect [9,10], the QCSE [7], and junction heating [11]. Among the above factors, poor hole injection in the active region and the resulting electron leakage are regarded as primary causes for this phenomenon [6,7].…”