Diffusion of Lithium into Ge and Si

Abstract

Lithium was diffused into Ge and Si at temperatures 300°−400°C and 400°−500°C, respectively. The diffusion was carried out in an inert gas atmosphere by decomposing LiAlH₄. The concentration of Li impurities as a function of depth from the surface of the sample was determined by lapping down thin layers of the diffused part of the sample and measuring the conductance of each of these thin layers. An erfc was chosen to fit the experimentally measured concentration curve from which the diffusion constant D for each temperature of diffusion was determined. The following dependence of temperature was found: $${\text{D=9.10×10}}^{\text{−3}}\exp \text{(−13100/RT)}\mathrm{for\; Ge}$$ , and $${\text{D=2.65×10}}^{\text{−3}}\exp \text{(−14500/RT)}\mathrm{for\; Si}$$ , where D is measured in cm²/sec, T in °K, and R=1.98 cal/°K. The deviation in the experimental values of D was not more than ±10% for Ge and ±20% for Si.