Techniques are described for growing (100) and (111) oriented CdTe on (100) oriented GaAs by molecular beam epitaxy. Structural characterization reveals that there are substantial differences in crystalline quality between the two orientations, (111) being superior. Single-crystalline (100) oriented films can be grown on oxidized GaAs surfaces, but the crystalline quality is improved if the oxide is desorbed prior to growth.

Single-crystal epitaxial layers of (100) and (111) oriented CdTe were grown on (100) oriented GaAs substrates by molecular beam epitaxy. Low-temperature (4.2 K) photoluminescence spectra exhibit free-exciton and bound-exciton peaks having linewidths on the order of 2 meV for both CdTe crystallographic orientations. However, defect-related photoluminescence is found to be stronger in (100) oriented CdTe.

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We report identification of a reliable p-type impurity dopant that can be used during molecular-beam-epitaxial (MBE) growth of HgTe-CdTe superlattices. Silver doping during the epitaxial growth of (100)-oriented HgTe-CdTe superlattices is shown to yield reproducible hole concentrations in the range of 1016–1018 cm−3. When normalized by the growth rate, the hole concentrations show an exponential dependence on the temperature of the Ag effusion cell. The diffusion of Ag in step-doped junctions was studied by use of secondary-ion mass spectrometry. The diffusion coefficient of Ag at the low MBE growth temperatures was found to be in the range of (1–5)×10−13 cm2/s. These values are comparable to recently reported values in MBE-grown (Hg,Cd)Te alloys and suggest that strain does not produce any new diffusion paths in the superlattices.

We report the observation of a broad photoluminescence line at 0.75 eV in CdTe grown by molecular-beam epitaxy at both high- and low-substrate temperatures. This line is in excellent agreement with the E2 line observed by deep-level transient spectroscopy by previous workers. The origin of both of these lines is probably a deep defect or impurity level native to CdTe.