Arsenic decapping and half cycle reactions during atomic layer deposition of Al 2 O 3 on In 0.53 Ga 0.47 As ( 001 )

In situ x-ray photoelectron spectroscopy was performed during thermal desorption of a protective As layer and subsequent atomic layer deposition (ALD) of Al 2 O 3 on In 0.53 Ga 0.47 As ( 001 ) . H 2 O dosing on the As-decapped surface caused formation of As oxides and As hydroxides, which were reduced by a subsequent trimethylaluminum (TMA) pulse. However, when a TMA pulse was performed first, the In 0.53 Ga 0.47 As ( 001 ) surface did not oxidize during subsequent ALD cycles, suggesting passivation by TMA adsorption at water-reactive sites. Scanning tunneling microscopy performed on a structurally-similar InAs(001) surface after H 2 O dosing revealed that surface defects are created by displacement of surface As atoms during oxidation. These surface defects act as interface states, consistent with the inferior capacitance-voltage characteristics of H 2 O -first ALD-Al 2 O 3 capacitors compared to TMA-first samples.