The influence of the substrate on the thermal stability of InGaAs/InGaAsP quantum wells

The effective band gaps of InGaAs/InGaAsP quantum wells can be modified after growth by interdiffusion at the boundaries between wells and barriers. The rate of interdiffusion is found to depend on the etch pit density (EPD) of the substrate used, with low EPDs leading to the most rapid diffusion and the largest decrease of the photoluminescence peak wavelength. InP substrates selected for their low EPD provide the maximum interdiffusion and hence the poorest control of quantum well properties. It is concluded that laser structures with sharper heterointerfaces and smaller changes of wavelength during heat treatment can be produced by growing on high EPD substrates.<>