Positron lifetime spectroscopic and photoluminescence techniques were used to investigate vacancy-related point defects in polycrystalline films that had been grown by means of chemical vapor deposition. It was found that undoped films contained large numbers of defects, including mono-vacancies, di-vacancies and vacancy clusters. These were distributed inhomogeneously throughout the films, with some crystallites being almost free of vacancies while others contained high (more than 50ppm) concentrations. However, B-doping could markedly reduce the vacancy content in the films. The vacancy-related defects were stable at up to 1100C. The various luminescence peaks were related to the different types of vacancy that were present in the chemical vapor-deposited material.

S.Dannefaer, W.Zhu, T.Bretagnon, D.Kerr: Physical Review B, 1996, 53[4], 1979-84