Formation of vacancy-impurity complexes in heavily Zn-doped InP

Positron annihilation spectroscopy has been applied to observe the spontaneous formation of vacancy-type defects by annealing of heavily Zn-doped InP at 500-700 K. The defect is identified as the V P -Zn pair by detecting the annihilation of positrons with core electrons. We conclude that the defect is formed through a diffusion process; a phosphorus vacancy migrates until trapped by a Zn impurity and forms a negatively charged Vp-Zn pair. The kinetics of the diffusion process is investigated by measuring the average positron lifetime as a function of annealing time and by fitting a diffusion model to the experimental results. We deduce a migration energy of 1.8′0.2 eV for the phosphorus vacancy. Our results explain both the presence of native Vp-Zn pairs in Zn-doped InP and their disappearance in post-growth annealings.