Half-cycle atomic layer deposition reaction studies of Al₂O₃ on (NH₄)₂S passivated GaAs(100) surfaces

“Half-cycle” atomic layer deposition reactions of trimethyl aluminum (TMA) and water on GaAs exposed to wet chemical sulfur treatments are studied for the formation of Al₂O₃. Trivalent oxides of gallium and arsenic are completely reduced following the first TMA pulse. The same processing step also removes As–S bonding below the level of detection, while the relative concentration of gallium suboxides as well as Ga–S bonds is not affected. A concomitant decrease in the S 2p peak intensity is observed, indicating that sulfur is lost through a volatile reaction product. Further precursor exposures do not measurably affect substrate surface chemistry.