The B diffusion in crystalline Ge was investigated under equilibrium and non-equilibrium conditions at 200 to 800C in order to discriminate the role of self-interstitials (Is) and the energy barriers involved in the microscopic mechanism of B migration. Numerous Is were produced by 200 or 300keV H+ irradiation and a direct comparison with B diffusion in thermal conditions at the same temperature was performed. The diffused profiles of B were simulated assuming the kick-out model, and the extracted parameters (migration length, λ, and formation rate of mobile B, g) indicated that the B diffusion was always mediated by Is showing different features at low and high T regimes. For T lower than 600C the thermal generation of Is was negligible and the only barrier to g (measured to be about 0.1eV) was due to the Is migration and B mobile formation. At T higher than 600C, the thermal generation of Is starts to overcome the Is supply from the irradiation, and the activation energy of g increased to 3.0 to 3.5eV. The migration length in the low-T regime had the largest value (about 20nm), while it decreased down to 1-2nm by increasing T, showing a negative activation energy of about -0.64eV, compatible with a dissociation process which stops the diffusion event. In this regard, it was observed that the mobile B migration length depended only upon T, regardless of the point defects concentration. These results and the energy barriers measurements contributed to an improved understanding of B diffusion and point defects in crystalline Ge.

Role of Self-Interstitials on B Diffusion in Ge. G.G.Scapellato, E.Bruno, A.J.Smith, E.Napolitani, D.De Salvador, S.Mirabella, M.Mastromatteo, A.Carnera, R.Gwilliam, F.Priolo: Nuclear Instruments and Methods in Physics Research B, 2012, 282, 8-11