Mechanisms behind efficiency droop and degradation in InGaN/GaN LEDs

Abstract

AbstractThe results of low frequency noise studies in power blue InGaN/GaN LEDs with external quantum efficiency 30‐45% classified by leakage current (LC) values before and after degradation are reported. The LC values at V< 2V integrally characterize electrical properties of extended defect system (EDS) that is typical for InGaN/GaN LEDs. The smaller concentration of extended defects and length of dilatation, dislocation boundaries, the lower LC value is. It has been demonstrated that non‐radiative recombination processes (NRRP) localized in extended defect system (EDS) contribute in efficiency droop of LEDs at j ≥ 10 A/cm2. The main characteristics of degradation processes such as: (1) increase in tunneling current values related with EDS, at U ≤ 2 V, (2) strong deterioration of p‐n junction rectification properties, (3) formation of conductive paths along EDS; (4) increase in non‐uniformity of current distribution, and (5) the formation of local overheating channels at j > 10 A/cm2 along EDS had been revealed. The NRRP are localized along EDS and can be considered as a general mechanism of efficiency droop and the ambiguous degradation process in power InGaN/GaN LEDs (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)