MOVPE growth of InGaAs/GaAsP-MQWs for high-power laser diodes studied by reflectance anisotropy spectroscopy

We have intensively studied the growth and strain behaviour of InxGa1−xAs multi-quantum wells (MQWs) for application in high-power laser diodes. Their growth in metal-organic vapour-phase epitaxy (MOVPE) was monitored by reflectance anisotropy spectroscopy (RAS). The influence of indium content variation in the InGaAs quantum wells and strain compensation using GaAsP layers on the reflectance anisotropy for single and multi-quantum wells has been studied. A clear dependence of the RAS signal on the indium and phosphorus content has been found. Furthermore, the beginning of strain relaxation during growth can be monitored by a difference in the RAS signals of the GaAs layers below and above the MQW structure. With optimised growth conditions complete laser structures have been grown. Laser diodes with very small far-field angles and different numbers of quantum wells were processed into broad-area lasers, which show output powers up to 60 W in pulse mode.