GROWTH AND CHARACTERIZATION OF GAAS ON SAPPHIRE (0001) BY MOLECULAR-BEAM EPITAXY

Crystal epilayers of (111)‐oriented GaAs have been grown successfully on sapphire (0001) substrates by molecular beam epitaxy. Although the epilayers were found to have a very high twin density, large areas (cm2) with no grain boundaries were observed. Both substrate surface preparation and temperature controlled the crystallinity. Reflection high‐energy electron diffraction (RHEED) was used to characterize the sapphire surface after ozone cleaning. RHEED patterns taken at several azimuths were consistent with an outermost layer of oxygen atoms. Powder x‐ray diffraction and rotation x‐ray photographs were used to determine growth conditions that resulted in an improvement in the crystalline order. Cross‐sectional transmission electron microscopy confirmed the crystalline nature of the GaAs epilayers. The quality of the GaAs was also characterized by photoluminescence. Finally, crystalline quality was assessed using double‐crystal x‐ray diffraction rocking curves. Copyright © 1990 John Wiley & Sons Ltd.