The impact of interstitials on diffusion in germanium under proton irradiation

Experiments on the influence of 2.5 MeV proton irradiation on self- and dopant diffusion in germanium (Ge) were performed at 600 and 570°C, respectively. Ge isotope heterostructures consisting of 20 layers were used for the self-diffusion study. Ge with boron (B) doped multilayers and samples implanted with phosphorus (P) were utilized for the investigation of irradiation mediated dopant diffusion. Self-diffusion under irradiation reveals an unusual homogenous broadening of the isotope structure. This behaviour and the enhanced diffusion of B and retarded diffusion of P under irradiation demonstrates that an interstitial-mediated diffusion process dominates in Ge under irradiation. This discovery establishes new ways to suppress vacancy-mediated diffusion in Ge and to solve the donor deactivation problem that limits Ge-based nanoelectronics.