Fourier-transform infra-red spectroscopic measurements were performed on undoped wafers of liquid-encapsulated Czochralski-grown material. The latter became semi-insulating upon annealing (800 to 900C) in a P ambient. The results revealed the presence of a high concentration of H complexes of the form, VInH4, before annealing. It was suggested that the predominant and essential process which led to the semi-insulating behavior was the compensation that was produced by an EL2-like deep donor P antisite defect which formed via dissociation of the H complexes during annealing. The deep donor compensated acceptors, most of which were shallow residual acceptor impurities and deep H-associated VIn and isolated VIn levels, were produced in the initial stages of the dissociation of a VInH4 complex. The high concentrations of In vacancies that were produced by the dissociation were the precursors of the EL2-like P antisite. This indicated the importance of H upon the electrical properties of InP, and showed that this resulted largely from the low formation-energy of the VInH4complex as compared with that of isolated VIn.

Y.W.Zhao, X.L.Xu, M.Gong, S.Fung, C.D.Beling, X.D.Chen, N.F.Sun, T.N.Sun, S.L.Liu, G.Y.Yang, X.B.Guo, Y.Z.Sun, L.Wang, Q.Y.Zheng, Z.H.Zhou, J.Chen: Applied Physics Letters, 1998, 72[17], 2126-8