Thermally-activated degradation of InGaN-based laser diodes: Effect on threshold current and forward voltage

Abstract

This paper presents a study of the effects of high temperature stress on the electro-optical characteristics of violet InGaN-based laser diodes. The results indicate that: (i) when submitted to constant current stress (with relatively high junction temperatures), devices show a significant increase in threshold current (Ith), related to the increase in non-radiative recombination; micro-cathodoluminescence measurements indicate that the area affected by degradation is wider than the ridge; (ii) the results of purely-thermal stress test indicate that the exposure to high temperature may induce an increase in threshold current; (iii) during the first part of the stress, this mechanism is well correlated with the variation of the forward voltage, suggesting a degradation in the properties (conductivity, acceptor doping) of the p-type material; for longer stress times, a further Ith increase is detected, with a linear dependence on time.