Stability of Oxides in High Purity Germanium

The thermochemical approach to reactions between dilute solutes is presented and applied to the stability of oxide second phases in the high purity germanium melt. Such oxide phases may degrade detector resolution and complicate purification. The equilibrium of oxygen between melt and gas allows both a convenient indication of the chemical potential of oxygen in the melt and a straightforward thermochemical calculation of reactions involving oxygen. For the range of oxygen (1013 - 1014 cm-3) and other impurity concentrations in high purity germanium no tabulated oxide is expected to be stable in the melt. If the concentration of oxygen in the melt is increased, the first important oxide phase to become stable is SiO2(1), strongly enriched with aluminum.