Thermal and Electrical Properties of Heavily Doped Ge-Si Alloys up to 1300°K

TLDR

The authors measured thermal resistivity, Seebeck coefficient, electrical resistivity, and Hall mobility of Ge–Si alloys across impurity concentrations 2×10^18–4×10^20 cm^−3 and temperatures 300–1300 K, and provided a qualitative interpretation of the trends. Boron and phosphorus proved effective p‑type and n‑type dopants, yielding maximum zT of 0.8 (p‑type Ge0.15Si0.85 at 2.1×10^20 cm^−3) and 1.0 (n‑type Ge0.15Si0.85 at 2.7×10^20 cm^−3) at 1200 K, and enabling a stable generator with a 10 % overall efficiency between 300–1200 K.

Abstract

The thermal resistivity, Seebeck coefficient, electrical resistivity, and Hall mobility of Ge-Si alloys have been measured throughout the Ge-Si alloy system as functions of impurity concentration in the range 2×1018−4×1020cm−3, and of temperature in the range 300°–1300°K. A qualitative interpretation of these properties is given. For power conversion, boron and phosphorus were found to be useful p-type and n-type impurities, respectively, because of their high solid solubilities. At 1200°K, the maximum values of the dimensionless figure of merit zT were 0.8 for p-type Ge0.15-Si0.85 alloy doped to 2.1×1020cm−3 holes, and 1.0 for n-type Ge0.15-Si0.85 alloy doped to 2.7×1020cm−3 electrons. The maximum over-all efficiency of a stable generator operating between 300°–1200°K, using the best p-type and n-type materials was computed to be 10%.