Influence of annealing on the properties of Ge:Sb/Si(001) layers with an antimony concentration above its equilibrium solubility in germanium

The influence of rapid thermal annealing on the electrical and radiative properties of Ge:Sb/Si(001) epitaxial layers with an antimony concentration substantially higher than its equilibrium solubility in germanium is investigated. Local variations in the electrical and luminescence properties of $n$-Ge/Si(001) throughout the structure depth are investigated by means of the precise chemical etching of Ge. It is shown that a variation in the properties of such layers at relatively low ($\le$ 500$^\circ$C) annealing temperatures (decrease in the electron concentration and photoluminescence intensity) occur in the absence of the noticeable diffusion-related redistribution of dopant atoms. Variations in the electrical and luminescence properties of Ge:Sb layers at relatively high ($\ge$ 700$^\circ$C) annealing temperatures are caused by the substantial redistribution of Sb due to its bulk diffusion and desorption from the surface. In particular, Sb diffusion leads to the formation of doped layers in initially undoped parts of the studied structures, which start to give a substantial contribution to the resulting conductivity of the structure and its photoluminescence signal.