The electronic structure of an Fe- and In-related center had been studied, by means of Fourier transmission infra-red spectroscopy, using uniaxial stress and polarization techniques. The center gave rise to an excitation spectrum which was centered at about 6550/cm, and was closely related to the orthorhombic FeIn pair center with an excitation spectrum at about 6100/cm. The 2 spectra were always observed in the Fe and In co-doped samples, and exhibited metastable properties which were similar to those reported for trigonal and orthorhombic FeIn pair centres. Uniaxial stress results were reported here which show unambiguously that the 6550/cm spectrum involved a center with trigonal symmetry. The polarization properties of the stress-split lines showed that the initial state of the transitions transformed in a manner which was identical to that previously deduced, for the trigonal FeIn center, by means of electron paramagnetic resonance. One of the excitation lines exhibited interesting polarization rules which were explained as a superposition of a σ and a π dipole at a C3v center. The spectrum was tentatively attributed to transitions from the deep ground state to shallow-like hole states. The symmetry of the center, and its ground state, strongly suggested that the center really was the trigonal version of the FeIn pair center.

Piezospectroscopy Study of the Trigonal FeIn Pair Center in Silicon P.Tidlund, M.Kleverman: Physical Review B, 1999, 59[23], 15208-13