Optical and structural properties of ZnSe/GaAs interfaces

The results of high resolution X-ray diffraction clearly show that the strain in the ZnSe films is inhomogeneous and depends only on the film thickness and not on the growth temperature in the range of 285-325°C; a value of approx. 0.17 μm is inferred for the critical thickness of ZnSe on GaAs. The measurements of the spectral response of the heterostructures give a strong photocurrent due to the absorption edges of both GaAs and ZnSe. However, in the case of the GaAs signal a shift towards lower energies is observed with the increase of substrate temperature, indicating local differences in the structure of the interfacial region. The analysis of the intensities of the LMM Auger transitions of Zn and Se indicates the formation of an interfacial layer with excess of Se, suggesting the formation of a pseudomorphic Ga2Se3 compound mixed with ZnSe at the interfacial region.