Controlled p-type impurity doping of HgTe-CdTe superlattices during molecular-beam-epitaxial growth

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.