Interactions between cleaved (Hg, Cd)Te surfaces and deposited overlayers of Al and In

The interactions between the clean, cleaved Hg0.72Cd0.28Te surfaces and thin evaporated layers of Al and In have been investigated with ultraviolet photoelectron spectroscopy using synchrotron radiation. Deposition of ultrathin layers of either metal was found to deplete the surface of much of its Hg by breaking the Hg-Te bonds to form a very thin interlayer of Al2Te3 or one of the several indium tellurides. In contrast, no interaction between the metals and the CdTe component was observed. Upon deposition of additional Al, a metallic Al overlayer was grown, with some Te diffusing to the surface. Some of the Hg freed by the initial reaction diffused into the semiconductor and formed a degenerate n+ layer capable of ohmically coupling n-type material to the metallic overlayer.