The microstructural reactions of PdGe in contact with n-type GaAs were investigated by using X-ray diffraction, Auger electron spectroscopy, and slow positron beams. The latter results showed that Ga vacancies were produced below PdGe during the formation of PdGe ohmic contacts. This implied the existence of n-GaAs layers, below PdGe, because the Ga vacancy concentration increased with the n-type impurity concentration. It was suggested that the n+-GaAs layer was a re-grown layer that arose from PdxGaAs, which contained excess Ge atoms, during annealing.

J.L.Lee, Y.T.Kim, J.S.Kwak, H.K.Baik, A.Uedono, S.Tanigawa: Journal of Applied Physics, 1997, 82[11], 5460-4