In0.53Ga0.47As(100) native oxide removal by liquid and gas phase HF/H2O chemistries
The native oxide removal, surface termination, and stoichiometry of InGaAs(100) 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 (100Torr, 29C, 0.5min) 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 5min of etching. As2O3 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.
native oxide removal gas phase hf ingaas liquid phase water surface preparation