Orientation of the electric-field gradient arising from a vacancy in Hg0.79Cd0.21Te

Abstract

We have used the perturbed angular correlation technique to measure the orientation of the electric-field gradients (EFGs) due to vacancy trapping by substitutional indium donors in the II-VI semiconductor Hg0.79Cd0.2Te. Previously, two hyperfine interaction frequencies were measured and were attributed to the trapping of a metal vacancy at a next nearest-neighbor site to the indium atom in bulk solid-state recrystallized materials. In the present experiments, measurements are done on thin-film samples to find the principal axes of the EFGs. Both EFGs are found to have principal axes parallel to a 〈111〉 crystal axis, despite the fact that a simple point charge model supports a 〈110〉 EFG for this 〈110〉-oriented In-VHg complex. A similar situation exists for indium-vacancy pairing in other II-VI semiconductors. We propose that the 〈111〉 EFG orientation arises from the electric dipole moments of the highly polarized Te ions in the region of the vacancy.