The temperature dependence of the anomalous Hall effects in p-type HgCdTe

Abstract

The anomalous Hall effects of narrow-band-gap p-type HgCdTe, which manifest themselves as negative Hall coefficients at low temperatures, have caused serious problems in material characterization in the past two decades. These phenomena are now widely recognized as being caused by the inverted surface effect describable by Petritz’s two-layer model [Phys. Rev. 110, 1254 (1958)]. We report results from variable-temperature Hall measurements on p-type HgCdTe liquid-phase epitaxy and bulk slices with bare, anodically sulfidized, and anodically oxidized surfaces. We show that the Hall anomalies can be eliminated by depositing an anodic sulfide layer on the surface and subsequently can be restored by removing the sulfide layer. Based on Petritz’s two-layer model, we were able to use the same set of bulk transport parameters and different sets of surface transport parameters to fit the experimental temperature-dependent Hall coefficient and Hall mobility curves of the same sample with surfaces that have been subjected to different chemical treatments. It was demonstrated that the Hall anomalies occurred when the n-type surface conductivity increased relative to the p-type bulk conductivity. The surface conductivity is mainly controlled by the density of fixed positive surface charges which was found to be larger on an anodically oxidized surface and smaller on an anodically sulfidized surface than on a bare surface.