Structural and Optical Studies of ZnCdSe/ZnSe/ZnMgSSe Separate Confinement Heterostructures with Different Buffer Layers

Abstract

Detailed structural and optical studies of ZnCdSe/ZnSe/ZnMgSSe separate confinement heterostructures (SCH) grown on ZnSe, ZnSe/ZnSSe strained-layer superlattices (SLS), and GaAs buffer layers at the II–VI/GaAs interface have been carried out by employing transmission electron microscopy, variable temperature photoluminescence (PL), and contactless electroreflectance (CER) measurements. A significant improvement on the defect reduction and the optical quality has been observed by using either the ZnSe/ZnSSe SLS or GaAs as the buffer layers when compared to that of the sample using only ZnSe as the buffer layer. However, the sample grown with the SLS buffer layers reveals a room temperature PL intensity higher than that of the sample grown with a GaAs buffer layer, which may still suffer from the great ionic differences between the II–V and III–V atoms. Using 15 K CER spectra, we have also studied various excitonic transitions originating from strained Zn0.80Cd0.20Se/ZnSe single quantum well in SCH with different buffer layers. An analysis of the CER spectra has led to the identification of various excitonic transitions, mnH (L), between the mth conduction band state and the nth heavy (light)-hole band state. An excellent agreement between experiments and theoretical calculations based on the envelope function approximation model has been achieved.