Self-consistent simulation of GaAs/InGaAs/AlGaAs heterostructures photoluminescence spectra and its application to pHEMT structures diagnostics

We performed numerical self-consistent solution of Schrödinger and Poisson equations for GaAs/InGaAs/AlGaAs pHEMT structures with quantum well. Based on the results we calculated optical transition matrix elements and photoluminescence spectra of such structures with the same design and different parameters (such as doping level and epitaxial layers width). In the photoluminescence spectra calculations three fitting parameters have been used. These parameters are GaAs/InGaAs valence band offset in strained quantum well, hole quasi Fermi level and inhomogeneous broadening. The PL peaks amplitudes and positions dependencies on the structure parameters were established. These dependencies can be used as the basis for pHEMT structure non-destructive diagnostics.

Catastrophic Optical Bulk Damage – A New Failure Mode in High-Power InGaAs-AlGaAs Strained Quantum Well Lasers

ABSTRACTHigh-power single-mode (SM) and multi-mode (MM) InGaAs-AlGaAs strained quantum well (QW) lasers with emission wavelengths of 910 − 980 nm are extensively used in various fiber lasers and amplifiers for both telecom and defense applications. In particular, underseas and satellite communication systems require stringent reliability from these lasers. Since these lasers predominantly fail by catastrophic and sudden degradation due to COD, it is crucial especially for space satellite applications to investigate reliability, failure modes, and degradation mechanisms of these lasers. Catastrophic optical mirror damage (COMD) was known to be the only failure mode until our group reported a new failure mode in MM and SM InGaAs-AlGaAs strained QW lasers in 2009 and 2016, respectively. Our group reported that bulk failure due to catastrophic optical bulk damage (COBD) has become the dominant failure mode of both SM and MM lasers. Since there have been limited reports on COBD compared to COMD, the intent of this paper is to introduce our studies on COBD that have spanned the last decade. We investigated reliability, failure modes, and degradation processes in SM and MM InGaAs-AlGaAs strained QW lasers by performing short-term step-stress tests and long-term accelerated life-tests as well as failure mode analyses using various nondestructive and destructive micro-analytical techniques including electron beam induced current (EBIC), time-resolved electroluminescence (EL), deep level transient spectroscopy (DLTS), focused ion beam (FIB), and high-resolution TEM. EBIC and EL techniques were employed to study dark line defects generated in degraded lasers stressed under different test conditions. Time-resolved EL techniques were employed to study initiation and progressions of dark spots and dark lines in real time as lasers were aged. DLTS techniques were employed to study electron traps in both pristine and degraded lasers. Lastly, FIB and high-resolution TEM were employed to prepare cross sectional and plan view TEM specimens to study DLD areas in post-aged lasers. We also report our current understanding on degradation mechanisms responsible for COBD in both SM and MM lasers.