ROLE OF GA2O IN THE REMOVAL OF GAAS SURFACE OXIDES INDUCED BY ATOMIC-HYDROGEN

The role of Ga2O in the removal of GaAs surface oxides induced by atomic hydrogen (H.) has been studied using temperature-programed desorption (TPD), x-ray photoelectron spectroscopy, and low-energy electron diffraction (LEED). GaAs(001) substrates with ''Ga2O3-like'' surface oxides formed in vacuo, as well as those ''as-loaded'' from air, were treated by thermally generated H. at substrate temperatures ranging from 210 to 410-degrees-C. Formation of Ga2O-like oxides was indicated by TPD performed after H. treatment. Above the onset temperature of Ga2O desorption, which was 350-400-degrees-C, oxide removal was rapid. Below the onset temperature, oxide removal was slow and incomplete, suggesting that Ga2O-like oxides act as a mask against H. irradiation. When treated by H. at 210-degrees-C, the amount of Ga2O-like oxides formed did not increase with the treatment time. Moreover, prolonged H. treatment at 210-degrees-C resulted in a Ga-rich LEED pattern. We attribute this to a further reaction of H. with Ga2O, resulting in Ga and water. In practice, H. treatment at temperatures above the Ga2O desorption onset is desirable for rapid and complete oxide removal, which results in a stoichiometric surface.