Migration Enhanced Epitaxy of GaAs Studied by Reflection High Energy Electron Diffraction and Scanning Tunneling Microscopy

Abstract

AbstractMigration enhanced epitaxy (MEE) of GaAs on (001) GaAs substrates was studied by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). In MEE, Ga and As species are alternately deposited on the growing surface. Ga adatom migration can be enhanced by the low arsenic pressure environment. The STM study was performed ex-situ by the arsenic capping and decapping procedure. We have demonstrated the correlation between the peak RHEED specular intensity during MEE growth and the variation of the lateral step density on the surface, even though the surface stoichiometry changes repetitively during MEE. The peak RHEED intensity during MEE is inversely dependent on the surface step density. The MEE surface exhibited a lower step density than the MBE surface, as shown by both RHEED and STM. However, the MEE surface still exhibited a much higher step density than a well-annealed surface. Consequently we believe that to achieve an atomically flat interface, annealing at high temperature in an arsenic flux is still necessary even if MEE is employed.