Root cause investigation of catastrophic degradation in high power multi-mode InGaAs-AlGaAs strained quantum well lasers

Optimization of broad-area InGaAs-AlGaAs strained-quantum-well lasers has led to successful demonstration of high power and high efficient operation for industrial applications. State-of-the-art broad-area single emitters show an optical output power of over 20W and a power conversion efficiency of over 70% under CW operation. However, understanding of long-term reliability and degradation processes of these devices is still poor. This paper investigates the root causes of catastrophic degradation in broad-area lasers by performing accelerated lifetests of these devices and failure mode analyses of degraded devices using various techniques. We investigated MOCVDgrown broad-area strained InGaAs-AlGaAs single QW lasers at ~975nm. Our study included both passivated and unpassivated broad-area lasers that yielded catastrophic failures at the facet and also in the bulk. Our accelerated lifetests generated failures at different stages of degradation by forcing them to reach a preset drop in optical output power. Deep-level-transient-spectroscopy (DLTS) was employed to study deep traps in degraded devices. Trap densities and capture cross-sections were estimated from a series of degraded devices to understand the role that point defects and extended defects play in degradation processes via recombination enhanced defect reaction. Electron-beam-induced-current (EBIC) was employed to find correlation between dark line defects in degraded lasers and test stress conditions. Time-resolved electroluminescence (EL) was employed to study formation and progression of dark spots and dark lines in real time to understand mechanisms leading to catastrophic facet and bulk degradation. Lastly, we present our physics-of-failure-based model of catastrophic degradation processes in these broad-area lasers.