IN-SITU CHARACTERIZATION OF II/VI MOLECULAR-BEAM EPITAXY GROWTH USING REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION OSCILLATIONS

The paper reviews the use of reflection high-energy electron diffraction (RHEED) oscillations to characterize molecular beam epitaxy (MBE) growth of II/VI wide-bandgap semiconductor materials. RHEED oscillations are routinely used in III/V crystal growth to measure growth rates and determine compositions. Their use in II/VI growth has been hampered by the difficulty in observing RHEED oscillations. However, with proper preparation of the crystal surface, oscillations are readily observable, and can be used to control growth and to investigate the physics of growth on the atomic layer scale. Several examples for II/VI MBE growth are examined in detail. Measurements of oscillations during the growth of ZnSe on deliberately misoriented substrates have led to an upper bound on surface diffusion of the II/VI; atoms. Measurements of the oscillations occurring during migration enhanced epitaxy (MEE) have been used to determine the amount of material deposited in each MEE cycle. Investigations of the characteristic shape of the oscillations have permitted development of a method to control composition of ZnSxSe1-x.