Electrical properties of <i>in situ</i> As doped Hg1−xCdxTe epilayers grown by molecular beam epitaxy

Abstract

The electrical properties of extrinsic in situ doped mercury cadmium telluride (Hg1−xCdxTe) epilayers grown by molecular beam epitaxy on (211)B CdTe/Si and CdZnTe substrates are studied. The doping is performed with an elemental arsenic source. HgCdTe epilayers with a CdTe mole fraction between 0.23 and 0.36 are grown at substrate temperatures of 175–185 °C. The temperature dependent Hall effect characteristics of the grown samples are measured by the van der Pauw technique. A magnetic field of up to 0.8 T is used in these measurements. An analysis of the Hall coefficient in the temperature range of 40–300 K with a fitting based on a two-band nonparabolic Kane model, a fully ionized compensating donor concentration, and two independent discrete acceptor levels is reported. In addition, the fitting results of a three-band modeling of Hall effect results are compared to published data on p-type Hg1−xCdxTe. Both as-grown and annealed samples are used in this study. All of the as-grown samples showed n-type characteristics whereas annealed samples showed p-type characteristics. The minority carrier lifetimes of arsenic doped epilayers measured by a photoconductive decay method are presented. In this work, an AlGaAs laser of wavelength 850 nm with a pulse length of 10–90 ns is used. The electron lifetimes obtained from this study are compared to published minority electron lifetimes in p-type HgCdTe. Theoretical electron lifetimes of p-type Hg1−xCdxTe material are reported and a comparison to published electron lifetimes is also given.