High Doping Activation (≥1020 cm–3) in Tensile-Strained n-Ge Alloys Achieved by High-Speed Continuous-Wave Laser Annealing

Abstract

Germanium-based materials are essential for the integration of Group IV optoelectronics in silicon devices. In addition to tensile strain, high n-type doping is critical, as it provides abundant carriers for recombination, potentially enabling higher photoemissions from Ge-based materials. We report here record-high 68% doping activation on n-Ge with ≥10²⁰ cm^–3 carrier density. This study centers on Sb-doped n-type Ge-on-insulator thin films with Si or Sn alloying grown using high-speed continuous-wave laser annealing (CWLA). Crystal mapping revealed the growth of polycrystalline n-GeSn and n-GeSi thin films with grain sizes up to 4 μm in diameter. Micro-PL measurements showed the PL intensity of n-Ge to be enhanced by the alloying of Sn and Si, with peak intensity 1.5 and 3 times higher for n-GeSn and n-GeSi, respectively. Raman peak red shift and broadening are observed in the samples, indicating high tensile strain and n-type doping. The measured carrier density of CWLA-grown films aligns well with the PL intensity trend, suggesting the process has promise for achieving electrically improved Ge-based thin films.