Local-vibrational-mode absorption of interstitial oxygen in GaP

Abstract

A local-vibrational-mode absorption line is measured at 1006.8cm−1 (T=7K) in GaP and identified as due to the antisymmetric stretching mode of interstitial oxygen (Ga–16Oi–P). The line due to 18Oi is found at 981.9cm−1. Uniaxial stress experiments indicate that the centre has a Cs(C1h) symmetry. For stress applied parallel to 〈001〉 direction, a low-temperature dichroism I||/I⊥>1 is observed. This is due to a low-temperature reorientation of the centre among its three equivalent configurations around a trigonal axis.