X-ray photoelectron spectroscopy study of oxide and Te overlayers on as-grown and etched HgCdTe

Abstract

X-ray photoelectron spectroscopy has been used to study the low-temperature (<80°C) preparation of HgCdTe surfaces with atomic hydrogen for the purpose of CdTe passivation. Atomic hydrogen was used to etch overlayers and surfaces of liquid phase epitaxy and molecular beam epitaxy HgCdTe, CdTe, HgTe, and Te. Oxide layers were easily removed, while carbon overlayers were resistant to atomic hydrogen etching at low temperature. Both Te and HgTe are etched by atomic hydrogen, with the HgTe etch rate about twice that of Te, while CdTe and ZnTe are not etched. Chemi-mechanical polishing of liquid phase epitaxy HgCdTe left a 10 to 20Å Te overlayer that could be removed with atomic hydrogen. In all cases, exposure of HgCdTe to atomic hydrogen led to surface composition shifts to higher x-value, with an x-value plateau near x∼0.6. All observations could be explained in terms of the formation of a 15Å surface layer of CdTe which blocks further etching.