Growth of pseudomorphic InGaAs/GaAs quantum wells on [111]B GaAs for strained layer, piezoelectric, optoelectronic devices

Abstract

Pseudomorphically strained InGaAs/GaAs quantum wells grown on [111]B oriented GaAs substrates incorporate strong piezoelectric fields. Quantum confined interband optical transitions exhibit built-in Stark shifts to the red and additional, ‘forbidden’ transitions are observed because of the reduced symmetry. The novel properties of these structures can be exploited in such devices as electro-optic modulators with increased sensitivity, blue-shifting self electro-optic effect devices (SEEDs) with enhanced contrast, all-optical symmetric SEEDs (SSEEDs) and pseudomorphic high electron mobility transistors (HEMTs) with increased two-dimensional electron gas (2DEG) densities. At all stages of research, development and production successful device work necessitates reliable material growth of good crystalline quality. High quality material is routinely obtained for wafers misoriented towards 〈211〉. For substrates misoriented towards the 〈211〉 direction good quality material can also be achieved, but only when great care is taken to ensure that growth is carried out within the narrower optimum growth window. With the help of this understanding we have been able to produce devices which have been used successfully to observe the predicted improvements.