The defect which corresponded to shallow etch pits on wafers was revealed. It was identified as being a vacancy-type Frank dislocation loop which surrounded a stacking fault. It was suggested that this loop formed, via the condensation of excess Ga vacancies, during cooling of the crystal. Precipitates of P on the dislocation loop resulted from the condensation of emitted P interstitials, accompanied by loop growth. Stoichiometry control was required in order to suppress the formation of shallow pit defects in low dislocation-density compound semiconductors.

The Origin of Shallow Etch Pit Defects in Low Dislocation Density GaP Crystals H.Okada, T.Kawanaka, S.Ohmoto: Journal of Applied Physics, 1999, 86[6], 3015-9