Chemical passivation of GaSb-based surfaces by atomic layer deposited ZnS using diethylzinc and hydrogen sulfide

The atomic layer deposition (ALD) of ZnS passivation nanofilms from diethylzinc and hydrogen sulfide is studied in the long-term chemical passivation of GaSb-based surfaces. The ZnS thin film growth is found to be linear with the number of deposition cycles from the beginning of the ALD of ZnS. Thioacetamide-(TAM) treated GaSb surfaces passivated without or with 1 nm-thick ZnS capping layer are investigated using x-ray photoelectron spectroscopy to study changes at the surface/interface of passivated GaSb surfaces over time. Immediately after TAM treatment or ZnS deposition, no oxides are found on the passivated surfaces. After exposure to atmospheric air for 14 days, the presence of gallium and antimony oxides in the ZnS capped TAM-treated GaSb is found to be significantly lower than that in samples treated only with TAM. Surface chemical passivation of TAM-treated InAs/GaSb structures with 1 and 2 nm-thick ZnS capping films are used to investigate the effect of film thickness on chemical passivation efficacy. The thicker ZnS film is found to provide better protection against oxidation by air as evidenced by the reduction of the corresponding oxide formation; these results indicate that oxygen diffusion through the ZnS is an important step in the long-term chemical passivation studies of GaSb-based nanostructures. Glancing incidence x-ray diffraction shows that the ZnS on TAM-treated GaSb is amorphous. (C) 2012 American Vacuum Society. [DOI: 10.1116/1.3669519]