Formation of PIn defect in annealed liquid-encapsulated Czochralski InP

Fourier transform infrared spectroscopy measurements have been carried out on liquid-encapsulated Czochralski-grown undoped InP wafers, which reproducibly become semi-insulating upon annealing in an ambient of phosphorus at 800–900 °C. The measurements reveal a high concentration of hydrogen complexes in the form VInH4 existing in the material before annealing in agreement with recent experimental studies. It is argued that the dominant and essential process producing the semi-insulating behavior is the compensation produced by an EL2-like deep donor phosphorus antisite defect, which is formed by the dissociation of the hydrogen complexes during the process of annealing. The deep donor compensates acceptors, the majority of which are shallow residual acceptor impurities and deep hydrogen associated VIn and isolated VIn levels, produced at the first stage of the dissociation of the VInH4 complex. The high concentration of indium vacancies produced by the dissociation are the precursor of the EL2-like phosphorus antisite. These results show the importance of hydrogen on the electrical properties of InP and indicate that this largely results from low formation energy of the complex VInH4 in comparison with that of an isolated VIn.