Identification of defects in undoped semi-insulating InP by positron lifetime

Positron lifetime measurements, carried out over the temperature range of 10-300 K, have been used to investigate defects in two undoped semi-insulating InP samples. The positron lifetime spectra were analysed by both PATFIT and MELT techniques. The results at room temperature reveal a positron lifetime of around 273ps, which is associated with indium vacancies V-In or V-In-hydrogen complexes. The positron average lifetime is temperature dependent and decreases with increasing temperature at the beginning (less than or equal to 80 K and less than or equal to 120 K), and then remains unchanged, which is attributed to the influence of negative vacancies and detrapping of the positron from those negative ions of Mg, Zn, Ag and Ca with ionization level (1-).