Solubility Interactions in Compensated, Heavily Doped Germanium

The solubility of the two donors, arsenic and antimony, in Ge at 870°C was enhanced by the acceptor dopant Ga at concentrations ≥ 10^19 cm^–3. The observed enhancement is in agreement with theory of the dopant-carrier ionization equilibrium in the Boltzmann approximation and confirms the requirement of the theory that the solubility enhancement depend only on the net carrier concentration and not on the chemical identity of the donor. A contrary result would have been likely, if donor-acceptor complexes played an important role in these solubility effects. The experimentally determined intrinsic carrier concentration at 870°C is ni = 1.8 × 10^19 cm^–3 compared to the extrapolated Hall value of ni ~1.3 × 10^19 cm^–3. The indicated extrinsic behavior implies that p-n junctions persist in very heavily doped germanium to the melting point.