I. Introduction
, a narrow band semiconductor is currently the leading material used for IR photo detection in the strategically important and windows1. Both thinned bulk crystals as well as epitaxial layers in the thickness range of are used in fabricating HgCdTe based photo-detector devices. Being a narrow gap semiconductor, HgCdTe is prone to have an easily accumulated2, depleted or inverted surface depending upon the surface treatments such as polishing, cleaning, etching and passivation. Therefore, the electrical properties of thin HgCdTe sheets are likely to be significantly altered from the bulk characteristics. In addition, HgCdTe is a multi-carrier system and extraction of bulk as well as surface properties is a tricky job and conventional fixed magnetic field Hall and resistivity measurements do not yield sufficient information. Earlier studies3,4,7 utilized variable magnetic field (B) Hall measurements as a tool to evaluate such conditions. However, this has been our observation that the fitting of variable B Hall data does not provide a unique fit for more than three carriers (nine parameters on the whole-three sets of carrier concentrations, mobilities and types). On the other hand we have observed that a simultaneous fitting of variable B Hall and magneto resistance data provides a more unique fit for at least up to four carriers. The same has been utilized in the present work to investigate the electrical characteristics of thin HgCdTe samples in the chemo-mechanically polished (bare) as well as anodic oxide (AO) passivated conditions. The anodic oxide over HgCdTe surface generally possess fixed positive3 charges and hence result in an accumulation layer in n-type samples. No definite behavior for the bare HgCdTe samples is, however, reported in the literature. The main idea was to identify and quantify the influence of surface charges on the sensitivity of variable magnetic field Hall measurements as well as their effect on the bulk electrical properties