Effects of annealing ambient on the formation of compensation defects in InP

Positron annihilation lifetime (PAL) and photoinduced current transient spectroscopies (PICTS) have been employed to study the formation of compensation defects in undoped InP under different annealing processes with pure phosphorus (PP) ambience and iron phosphide (IP) ambience, respectively. The different annealing ambiences convert the as-grown n-type undoped InP into two types of semi-insulating (SI) states. The positron average lifetimes of as-grown InP, PP SI-InP, and IP SI-InP are found to be 246, 251, and 243 ps, respectively, which are all longer than the bulk lifetime of 240 ps, indicating the existence of vacancy-type positron-trapping defects. For as-grown InP, VInH4 complexes are the dominant defects. They dissociate into VInHn(0⩽n⩽3) acceptor vacancies under PP ambience annealing, compensating the residual shallow donors and turning the material semi-insulating. In forming IP SI-InP, diffusion of iron into VIn complexes under IP ambience annealing produces the substitutional compensation defect FeIn, causing a shorter positron average lifetime. The PICTS measurements show that a group of vacancy-type defects has been suppressed by iron diffusion during the annealing process, which is in good agreement with the PAL results.