Reliability and degradation mechanisms in high-power broad-area lasers with strained InGaAs-AlGaAs QW and InAs-GaAs QD active regions

Abstract

High-power InGaAs-AlGaAs strained quantum well (QW) lasers are indispensable components for both terrestrial and space satellite communications systems. However, their degradation mode (catastrophic and sudden degradation) due to catastrophic optical damage is a major concern for space applications. Furthermore, these lasers predominantly degrade by a new failure mode due to catastrophic optical bulk damage (COBD). Also, InAs-GaAs quantum dot (QD) lasers have recently received much attention as an alternative to QW lasers especially for space applications, but their degradation mechanism is not well understood. For the present study, we investigated 9×× nm broad-area strained QW lasers and ~ 1 μm broad-area QD lasers. QW lasers were consisted of an InGaAs QW layer, while QD lasers were consisted of ten stacks of InAs QD layers. As part of our root causes investigation to understand degradation mechanisms in InGaAs-AlGaAs strained QW lasers as well as in InAs-GaAs QD lasers, we performed short-term and long-term life-tests, failure mode analyses, and physics of failure investigations using various techniques. First, we employed electroluminescence techniques to study the formation of dark line defects (DLDs) in degraded lasers. Second, time-resolved electroluminescence (TR-EL) techniques were employed to study the formation and propagation of dark spots and dark lines in window QW lasers in real time during aging. Third, we employed deep level transient spectroscopy (DLTS) and time-resolved photoluminescence (TR-PL) techniques to study a role that electron traps and non-radiative recombination centers (NRCs) play in degradation of these lasers. Finally, we report our understanding on mechanisms responsible for degradation in high-power QW lasers and preliminary results from QD lasers.