Photoquenching effect and its consequence in p type gallium arsenide

In order to examine the origin of the occasionally observed shift in the photoconductivity peak with respect to the band gap value; optical and electro-optical investigation of a p type GaAs crystal was carried out. The absorption and photochonductivity spectra were recorded and by comparing both spectra, a model based on the transition of electrons from the oxygen “adsorbate surface states” is proposed to explain the strong photoquenching observed on the high energy side of the band gap value. This also explains the observed shift.