Self-diffusion in intrinsic germanium and effects of doping on self-diffusion in germanium

Abstract

Self-diffusion in intrinsic germanium single crystals has been investigated over the temperature range 822-1163K using 71Ge as radioisotope and a sputtering technique for serial sectioning. The data can be described by a preexponential factor of (2.48+or-0.6)*10-3 m2 s-1 and an activation enthalpy of (3.14+or-0.92) eV. The present data are discussed together with literature data obtained with conventional sectioning techniques at higher temperatures. The self-diffusion coefficients at 870 and 894K were also measured for Ga-doped (1.7*1018 atoms cm-3) and Sb-doped (1.8*1018 atoms cm-3) samples. The diffusivity is higher in n-type and lower in p-type germanium than in intrinsic material. Since it is known that a vacancy in germanium acts as an acceptor the observed direction and order of magnitude of the doping dependence can be understood in terms of the shift of the Fermi level in doped crystals. This supports the view that self-diffusion in germanium proceeds by a vacancy mechanism.