Electrically active defects induced by hydrogen and helium implantations in Ge

Abstract

Results of a study of electrically active defects induced in Sb-doped Ge crystals by implantations of hydrogen and helium ions (protons and alpha particles) with energies in the range from 500 keV to 1 MeV and doses in the range 1×10 10–1×10 14 cm −2 are presented in this work. Transformations of the defects upon post-implantation isochronal anneals in the temperature range 50–350 °C have also been studied. The results have been obtained by means of capacitance–voltage ( C– V) measurements and deep-level transient spectroscopy (DLTS). It was found from an analysis of DLTS spectra that low doses (<5×10 10 cm −2) of H and He ion implantations resulted in the introduction of damage similar to that observed after MeV electron irradiation. The Sb–vacancy complex was the dominant deep-level defect in the lightly implanted samples. After implantations with doses higher than 5×10 10 cm −2 peaks due to more complex defects were observed in the DLTS spectra. Implantations with heavy (⩾5×10 13 cm −2) doses of both H and He ions caused the formation of a sub-surface layer with a high (up to 1×10 17 cm −3) concentration of donors. These donors were eliminated by anneals at temperatures in the range 100–200 °C. Heat treatments of the heavy proton-implanted Ge samples in the temperature range 250–300 °C resulted in the formation of shallow hydrogen-related donors, the concentration of which was the highest in a region close to the projected depth of implanted protons. The maximum peak concentration of the H-related donors was higher than 1×10 15 cm −3 for a proton implantation dose of 1×10 14 cm −2.