Correlations between DLTS and EPR measurements of the Ga vacancy in GaP

Abstract

Correlations between a DLTS peak labelled I2 and an EPR spectrum labelled NRL-1 and attributed to the Ga vacancy in electron-irradiated GaP are examined to determine whether the defect responsible is the same. Previous work on this question is updated to include the finding that NRL-1 has spin S=3/2 and new results on the capture cross-section sigma h for I2. The value of sigma h at 279K, 5*10-17 cm 2, suggests that there is hole capture by a neutral state. Correlations between I2 and NRL-1 are good for the annealing temperature and charge state. The measured introduction rates for each are different, but can be reconciled. There is consistency between the energy level for I2, Ev+0.64 eV, and inferences drawn from the EPR results. However, based on current theoretical predictions of energy level spacings, a second peak from the vacancy is expected in the DLTS data. DLTS data show a minority-carrier trap which can be ascribed to this second vacancy level.