Comparison of the photocurrent of ZnSe/InSe/Si and ZnSe/Si heterojunctions

A thin (≈200 nm) ZnSe film was grown by molecular beam epitaxy on p-type Si with an InSe buffer layer in between. The InSe buffer (≈25 Å) was used to bypass the huge lattice mismatch of 4.4% between ZnSe and Si in order to ensure the growth of stress-free ZnSe. The ZnSe/InSe/Si heterojunction exhibited rectifying features and intrinsic photoconductivity. It happens, however, that the shape of the photocurrent spectrum differs considerably from those of ZnSe/Si heterojunctions. The differences are explained by enhanced transport and diffusion features of excited electrons in the Si substrate due to the relaxation at the interface in comparison with ZnSe/Si samples.