AN OPTICAL STUDY OF ENCAPSULANT THICKNESS-CONTROLLED INTERDIFFUSION OF ASYMMETRIC GAAS QUANTUM-WELL MATERIAL

The study uses photocurrent spectroscopy and luminescence techniques to investigate the effect of interdiffusion on a GaAs/AlGaAs system with four quantum wells. The wells are non-identical in that the two central wells have equal (symmetric) Al barriers, while the outer two have unequal (asymmetric) ones. This results in the magnitude of the spectral blue-shift induced by the interdiffusion being different for the two well configurations. Investigations are carried out into the response of the two well types to differing levels of interdiffusion. The interdiffusion is brought about by capping with SiO2 followed by annealing, and we show that the extent of the interdiffusion can be controlled by the thickness of the encapsulant, and that the effect saturates for thicker caps.