Implantation of Bi into GaP III. Hot-Implant Behavior

Abstract

Channeling and photoluminescence are studied in GaP implanted with Bi at an elevated temperature (450°C), and comparison is made with samples implanted at room temperature (25°C) and subsequently annealed at 450 °C. It is found that the channeling behavior is significantly improved by the hot implant, and that the Bi is ~75% substitutional. However, no photoluminescence is observable unless the samples are annealed at temperatures in excess of 600 °C. After annealing at 800 °C, the luminescence intensity obtained from the hot-implant samples is compared with those implanted at room temperature, for doses of 2 · 10¹³ and 1.8-10¹⁵ Bi ions/cm². For the low-dose case, hot implants increase the luminescence by only ~8%, whereas the weak luminescence observed from the high-dose samples increases by ~65%. The spectral features of the luminescence provide evidence for the presence of both strain and competing damage centers. A detailed study of the channeling angular distribution indicates that the low optical efficiencies cannot be explained by assuming that a substantial fraction of the implanted Bi ions occupy substitutional Ga sites, where they would be optically inactive.

On leave from University of the Witwatersrand, Johannesburg, South Africa.