Ion-channeling and optical absorption studies of implantation disorder in germanium

Abstract

Ion-channeling and optical absorption measurements are reported for lattice disorder in Ge after ion implantation at 90 K. An anneal stage is observed by ion channeling at 175 K for low-fluence Zn implants (3×1012/cm2). The annealing occurs over a much narrower temperature range (∼50 K) than is observed for low-temperature implantation disorder in Si. The Ge anneal stage measured by ion channeling is shown to correlate closely with that observed by near-band-edge optical absorption measurements for these low-disorder-density implants. For high-disorder-density implants (e.g., ≳3×1013 Zn/cm2) ion-channeling measurements saturate due to a loss of long-range order, while near-edge absorption measurements are still sensitive to further changes in the disorder. Following high-disorder-density implants near-edge absorption shows appreciable recovery below room temperature, while ion channeling shows recovery of the long-range order at temperatures ≳450 K. Thus, ion-channeling and optical absorption measurements of ion-induced disorder in Ge are shown to correlate for low-disorder-density implants and provide complementary information for high-disorder-density implants.