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

The study uses photocurrent spectroscopy and luminescence techniques t o investigate the effect of interdiffusion on a GaAs/AlGaAs system wit h four quantum wells. The wells are non-identical in that the two cent ral wells have equal (symmetric) Al barriers, while the outer two have unequal (asymmetric) ones. This results in the magnitude of the spect ral blue-shift induced by the interdiffusion being different for the t wo well configurations. Investigations are carried out into the respon se of the two well types to differing levels of interdiffusion. The in terdiffusion is brought about by capping with SiO2 followed by anneali ng, and we show that the extent of the interdiffusion can be controlle d by the thickness of the encapsulant, and that the effect saturates f or thicker caps.