In_0.53Ga_0.47As(1 0 0) native oxide removal by liquid and gas phase HF/H₂O chemistries

The native oxide removal, surface termination, and stoichiometry of InGaAs(1 0 0) surfaces using liquid and gas phase HF/H₂O etching were studied using X-ray photoelectron spectroscopy. Oxide removal in liquid phase HF stopped at the As layer, producing either elemental or H-terminated As. The surface oxidized upon air exposure, forming a 4.8 As₂O₃ layer on an As rich InGaAs sub-surface (17% In, 16% Ga, 66% As). A sub atmospheric gas phase HF/H₂O process (100 Torr, 29 °C, 0.5 min) completely removed As₂O₃ and produced mainly In and Ga fluorides, since As fluoride is volatile at these experimental conditions. Once enough F accumulated on the surface, the water sticking probability decreased and the etching reaction proceeded at a much lower rate. The highest oxide removal (4.2 residual oxide) was achieved after 5 min of etching. As ₂O₃ and As₂O₅ were completely removed and considerably more InF₃ and GaF₃ were produced. The surface contained a group III-fluoride rich overlayer (34% In, 36% Ga) on a slightly As rich bulk (21% In, 21% Ga, and 58% As). The As rich InGaAs sub-surface produced with both liquid and the longer gas phase HF treatments is intrinsic to HF-InGaAs chemistry, although the oxide removal mechanism is likely different.