Ex-situ XPS-investigation of the interface between PE-CVD SiO2 and wet chemically etched MO-CVD epitaxial layers of In0.53Ga0.47As

The As rich SiO₂/In_0.53Ga_0.47As interface which is produced by wet chemical etching before SiO₂ deposition to improve the electronic properties of the interface has been studied. SiO₂-layers of about 10 to 20 nm thickness have been deposited in a plasma enhanced chemical vapour deposition (PECVD) reactor and then thinned down to about 4 to 3 nm by 1.5 keV Ar ion beam bombardment at grazing incidence (85°) in the XPS analysis chamber. The photoelectron spectra show that an additional broadening of the In and As lines due to a possible ion beam damage can be neglected in case of a qualitative interpretation of the interface spectra. Moreover, TRIM simulations of the collision cascade reveal low damage production in the SiO₂/In_0.53Ga_0.47As interface region. Therefore such ex-situ XPS experiments allow a supervision of the interface chemistry after the fabrication process and an optimisation of the technology with regard to the etching solution and deposition conditions. The conservation or removal of the elemental arsenic and the oxidation of the semiconductor due to the SiO₂ deposition are well reflected in the photoelectron spectra.