SURFACE-DIFFUSION DURING MOLECULAR-BEAM EPITAXY GROWTH OF ZNSE STUDIED BY REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION

We report the use of reflection high-energy electron diffraction (RHEED) oscillations to characterize surface diffusion during ZnSe crystal growth by molecular-beam epitaxy (MBE). For GaAs growth on vicinal (001) surfaces, RHEED oscillations disappear above a certain substrate temperature, indicating that the Ga diffusion length exceeds the step terrace width. However, for ZnSe, we observe RHEED oscillations over the entire range of substrate temperatures (250-400-degrees-C) typically used during MBE growth. The diffusion length of Zn and/or Se is determined to be less than 40 angstrom. The slow diffusion of Zn and/or Se that we observe can explain the general difficulty in observing RHEED oscillations during ZnSe growth, and has implications for interface roughness in heterostructures containing ZnSe layers.