An explanation for invalidity of working currents' derating on improving light-emitting diode devices' reliability

Abstract

Derating of the working current level does not work for improving GaN-based light-emitting diode (LED) devices' reliability. The present work demonstrates that it is not the levels but the specific components of the applied electrical currents weighing more on LEDs' degradation. Existing defects are sources for tunneling currents and Shockley-Read-Hall (SRH) non-radiative recombination current, and the component of tunneling currents and SRH non-radiative recombination current in the applied electrical current will in turn induce fast increase of defect density. The current component from electron tunneling to deep levels in the vicinity of mixed/screw dislocations will affect more on LEDs' degradation than other components, such as heavy-hole tunneling via intermediate state. In a whole, the overflow leakage current from the active region and Auger recombination currents in the applied electrical current will generate positive effects to alleviate LEDs' degradation.

Physics‐based modeling and experimental implications of trap‐assisted tunneling in InGaN/GaN light‐emitting diodes

“…Since the sub‐threshold forward‐bias current is a sensitive indicator of growth quality, device reliability and ESD robustness , the improvement of its physical understanding and the demonstration of reliable physics‐based approaches for its simulation are important for LED technology optimization. The aim of this study was to investigate the relative relevance of several trap‐assisted electron tunneling mechanisms in a single‐quantum‐well LED test structure.…”

“…The important role of defects and tunneling in the electrical behavior of InGaN/GaN LEDs has been pointed out in a large number of studies . However, most contributions deal with indirect considerations about defect‐assisted tunneling mechanism stemming from the analysis of the forward I ( V ) characteristics measured at different temperatures and, in particular, of the high ideality factors η observed at low bias.…”

Effect of high-temperature/current stress on the forward tunneling current of InGaN/GaN high-power blue-light-emitting diodes

“…8) There are also some works focused on the investigation of the specific impact of a certain component of forward current on the reliability and performance of LEDs. [13][14][15] For example, Liu et al reported that electron tunneling current affects device reliability more than any other forward current component. 13) In this work, we first investigated the forward carrier transport mechanism of InGaN=GaN high-power blue LEDs grown on sapphire through the analysis of temperaturedependent I-V characteristics.…”

Modeling challenges for high-efficiency visible light-emitting diodes

“…The high ideality factor experimentally observed below the optical turn-on of GaN LEDs [19] is the hallmark of trap-assisted tunneling (TAT). Through its signature on the sub-threshold forward-bias characteristics, TAT may represent a useful indicator of the presence of defects and then, in turn, of device growth quality [20] or degradation due to accelerated stress testing [21]. But the importance of TAT does not seem to be limited to the sub-threshold regime; for example, reports attempting to peg the efficiency degradation to TAT have been presented by [22][23][24].…”