Low-temperature spectral CL study of growth-induced defects in butt-coupled strain compensated InGaAs/InGaAsP/InP MQW amplifier-waveguide devices for semiconductor optical amplifiers

Butt-coupled InGaAs/InGaAsP/InP multi-quantum-well (MQW) based amplifier-waveguide devices for semiconductor optical amplifiers (SOAs) were studied by spectral cathodoluminescence (SCL) at T=77K. The following growth-induced defects were observed: (1) a significant grading of the waveguide composition (up to similar to 160 meV), occurring up to similar to 200 mum from the amplifier-waveguide interface due to perturbations of the gas flow dynamics and surface kinetics of the regrowth process, caused by the Si based dielectric mask (2) etch residues of the MQW material inside the waveguide region due to poor etch selectivity and (3) multiple MQW emissions and variations of the MQW composition along the ridge due td temperature and/or flux instabilities during the growth.