Fermi-level movement at metal/HgCdTe contacts formed at low temperature

Abstract

In an effort to reduce the disruption to the HgCdTe surface upon metal overlayer formation over that observed at room temperature, interfaces formed at 100 K between HgCdTe and the three overlayer metals, Ag, Al, and Pd, are investigated. The metals were deposited onto the [110] cleaved HgCdTe surfaces in UHV in increments ranging from submonolayer at low coverages to tens of monolayers at high coverages, and the formation of the interfaces were monitored using photoemission spectroscopy subsequent to each deposition. The primary experimental observation of this study is that deposition of all three of these metals onto HgCdTe substrates held at reduced temperatures causes the surface Fermi level (Ef) to move from its initial cleaved position, typically located at or near the conduction-band minimum, into the conduction band, and this movement is correlated with the absence of the movement of the overlayer metal into the semiconductor. This phenomenon is observed at the lowest coverages (submonolayer) for all three overlayer metals, and for the case of Ag grown at 100 K, is observed for higher coverages as well. The final positions of Ef for the three overlayer growths match very closely to those seen for the corresponding room-temperature growths.