The perturbed angular correlation technique was used to measure the orientations of the electric field gradients which were due to vacancy trapping by substitutional In donors in the II-VI semiconductor, Hg0.79Cd0.2Te. Previously, 2 hyperfine interaction frequencies had been attributed to the trapping of a metal vacancy at next-nearest neighbors to In atoms in bulk solid-state recrystallized materials. Here, measurements were performed on thin-film samples in order to identify the principal axes of the electric field gradients. Both gradients were found to have principal axes which were parallel to a <111> crystal axis, although a simple point charge model predicted a <110> electric field gradient for this <110>-oriented In-VHg complex. A similar situation existed with regard to In-vacancy pairing in other II-VI semiconductors. It was proposed that the <111> electric field gradient orientation arose from the electric dipole moments of highly polarized Te ions in the vicinity of the vacancy.

W.C.Hughes, J.C.Austin, M.L.Swanson: Journal of Applied Physics, 1993, 74[8], 4943-7