Enhanced equilibrium concentration of donors in antimony- arsenic- or phosphorus-doped silicon on sapphire

Abstract

This work reports the equilibrium values of the electron density, as a function of the annealing temperature, in epitaxial silicon films on sapphire saturated with antimony or arsenic. The reported equilibrium values were determined in the dissolution stage of the precipitates in the temperature ranges 900–1250 °C for antimony-doped specimens and 750–1150 °C for arsenic-doped specimens. These electron density values in epitaxial silicon films on sapphire markedly exceed those at the solubility limit in silicon, which were determined previously by the same method. The same phenomenon is observed in phosphorus-doped specimens. Further experiments were performed on silicon wafers saturated with antimony, after addition of aluminium and oxygen by ion implantation and subsequent annealing at 1100 °C. The addition resulted in an increase in the electron density thus showing that the phenomenon observed in epitaxial silicon films on sapphire is due to the dissolution of the sapphire constituents into the epitaxial silicon film.