Catastrophic optical bulk damage (COBD) in high power multi-mode InGaAs-AlGaAs strained quantum well lasers
2011
State-of-the-art broad-area InGaAs-AlGaAs strained quantum well (QW) lasers show an optical output power of
over 20 W and a power conversion efficiency of over 70% under CW operation. Unlike broad-area (Al)GaAs QW
lasers, broad-area InGaAs strained QW lasers show two failure types including facet catastrophic optical damage
(COD) and bulk failure. Optimization of facet passivation processes has led to significant reduction in occurrence of
facet COD (or COMD), but bulk failure (or COBD) has received little attention although it is crucial to understand
degradation processes responsible for COBD and then develop COBD-free lasers for high reliability applications
including potential satellite systems. Our group recently proposed a model for the COBD process and this paper
further investigates the root causes of COBD in the broad-area lasers. We performed accelerated life-tests of
MOCVD-grown broad-area strained InGaAs-AlGaAs single QW lasers at ~975 nm, which predominantly yielded
catastrophic bulk failures. We employed various non-destructive techniques to study pre- and post-stressed lasers.
Time resolved electroluminescence (TR-EL) was employed to observe formation and progression of dark spots and
dark lines through windowed n-contacts during entire life-tests that eventually led to COBD. Deep level transient
spectroscopy (DLTS) was employed to investigate trap characteristics in degraded devices at different stages of
degradation to study the role that non-radiative recombination centers (NRCs) play in COBD processes. Time
resolved photoluminescence (TR-PL) was employed to measure carrier lifetimes from both undamaged and
damaged active areas to find correlation between dark line defects in degraded lasers and non-radiative
recombination processes.
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