Observation of extremely large sheet hole densities in uncapped undoped AlSb layers

In this paper, we present a study of the electrical and physical properties of uncapped AlSb, grown by molecular beam epitaxy. Large concentrations of oxygen have been observed in the uncapped undoped AlSb layers, resulting in extremely large sheet hole densities (as high as 3/spl times/10/sup 15/ cm/sup -2/ with the corresponding mobilities of about 60 cm/sup 2/V/sup -1/s/sup -1/). However, for the AlSb layers capped with 50 /spl Aring/ of GaSb, oxygen does not penetrate beyond the GaSb cap layer, and the underlying AlSb layer is highly resistive. X-ray photoelectron spectroscopy (XPS) has been used to analyze the surface oxides for the uncapped AlSb layers. Three different oxides have been observed on the surface of the uncapped layers: Al/sub 2/O/sub 3/, Sb/sub 2/O/sub 5/, and Sb/sub 2/O/sub 3/.< >