Growth of InGaAs/AlAsSb single quantum wells with various AlAs diffusion-stopping layers

We have grown InGaAs/AlAsSb single quantum wells (SQWs) with AlAs diffusion-stopping layers of various thicknesses by molecular beam epitaxy. X-ray diffraction rocking curve measurements as well as optical microscope observations indicated good structural quality of the samples having less than 4-monolayer (ML) AlAs layers, which were inserted between InGaAs wells and AlAsSb barriers. Near-infrared absorption measurements revealed that when only 2-ML AlAs layers were inserted at the interfaces, the absorption coefficient of intersubband transition in the conduction band was significantly enhanced, and the peak wavelength was greatly shifted toward shorter wavelengths. This improvement in the optical quality confirms that thin AlAs layers efficiently reduce atomic interdiffusion at the interfaces. The results of the absorption measurements also suggest that such interdiffusion occurs more readily at the lower interface of the InGaAs well than at the upper interface.