Positron annihilation lifetime and positron annihilation Doppler broadening spectroscopy were used to investigate the formation of vacancy-type compensation defects in n-type undoped liquid encapsulated Czochralski grown InP, which undergoes conduction-type conversions under high temperature annealing. N-type InP became p-type semiconducting by short time annealing at 700C, and then turns into n-type again after further annealing but with a much higher resistivity. Long time annealing at 950C makes the material semi-insulating. Positron lifetime measurements showed that the average positron lifetime increase from 245ps to a higher value of 247ps for the first n-type to p-type conversion and decreases to 240ps for the ensuing p-type to n-type conversion. The value of the average positron lifetime increased slightly to 242ps upon further annealing and attains a value of 250ps under 90h annealing at 950C. These results together with those of positron-annihilation Doppler-broadening measurements were explained by the model proposed in a previous study. The correlation between the characteristics of positron annihilation and the conversions of conduction type indicated that the formation of vacancy-type defects and the progressive variation of their concentrations during annealing were related to the electrical properties of the bulk InP material.

Positron-Annihilation study of Compensation Defects in InP. Y.Y.Shan, A.H.Deng, C.C.Ling, S.Fung, C.D.Ling, Y.W.Zhao, T.N.Sun, N.F.Sun: Journal of Applied Physics, 2002, 91[4], 1998-2001