Molecular beam epitaxial growth and evaluation of intrinsic and extrinsically doped Hg0.8Cd0.2Te on (100) Cd0.96Zn0.04Te

Abstract

The structural and electrical properties of (100) Hg1−xCdxTe epilayers grown by molecular beam epitaxy have been systematically investigated for different Hg/Te flux ratios. The hillock density, electron concentration and the electron mobility depend strongly on the Hg/Te flux ratio. A minimum in the hillock density correlates well with the highest mobilities and the lowest concentrations. As is well known electrical properties are strongly influenced by structural defects. Structural defects such as twins and defects due to nonstoichiometry can be largely reduced by optimizing the Hg/Te flux ratio. It is shown that an optimum Hg/Te flux ratio exists within a narrow range between 270 and 360 at the growth temperature of 180 °C, in contrast with the larger range of the Hg/Te flux ratio over which single crystalline growth could be maintained. The difficulties encountered in the x value determination from normal transmission curves, i.e., from E0(x), due to the Burstein–Moss shift are discussed. In order to overcome these difficulties, the x values of the Hg1−xCdxTe epilayers were also determined from E1(x). A calibration of E1(x) resulted in small but significant discrepancies with the literature. Extrinsic As doping using the δ doping technique is demonstrated and a very high atomic sheet density of 1.2×1013 cm−2 is obtained.