Degradation of InGaN-based laser diodes analyzed by means of electrical and optical measurements

Abstract

In this paper we present a detailed analysis of the degradation of InGaN-based laser diodes carried out by means of electrical and optical techniques. The study is based on the comparison between the degradation kinetics of laser diodes and light-emitting diode LED-like samples, i.e., devices with the same epitaxial structure as the lasers, but with no ridge and facets. Results described in the following indicate that degradation of lasers and LED-like samples is due to the same mechanism, possibly involving the generation of point defects within the active region of the devices. Furthermore, since degradation occurs both in lasers and in LED-like samples i.e., structures with no current confinement, results suggest that degradation of lasers is not correlated with the geometry of the devices, nor to worsening of current confinement under the ridge

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…It was found that in blue MQW GaN/InGaN LEDs with degradation times from some minutes to some 10 h two degradation mechanisms were prevalent: (1) the formation of dislocation bunches in the (0 0 0 1) plane (and associated increase in non-radiative recombination), and (2) increased nonuniformity of injection in p-n junctions [374]. For MOCVD LDs and LEDs perhaps the most insightful studies were reported in papers [370,372]. The authors performed measurements of degradation parameters in MQW LDs and LED-like structures, both prepared on the same epitaxial wafers and differing by the presence of the ridge and mirror facets in lasers (absent in LED structures).…”

“…Refs. [370][371][372]). For MOCVD-grown LEDs and LDs with low dislocation density grown by ELOG [369] or using low-dislocation density GaN substrates grown by high pressure technique [371] no formation of additional dislocations during degradation was noticed.…”

Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

“…The first demonstration of emission in GaN-based laser diode was reported in 1996 by Nakamura [139,140]. Still, their maximum optical power, lifetime and reliability are strongly limited by degradation processes induced mainly by increase of the temperature in the particular parts of the laser: facet, active layers or contacts [141][142][143]. Typical degradation mechanisms known from arsenide based devices (like COMD or DLD) are not responsible for failure of GaN based diodes.…”

Thermal Analysis of Blue Laser Diode for Solid State Lighting Application

“…Common problem of SSL based on semiconductors is their heating [6] [7] [8], when the current increases. It doesn't concern only lighting domain, but also data storage or communication, when coupling of laser and phosphor is used [9] [10].…”