Experimental evidence of impurity-band transport in p-type polycrystalline germanium film

Herein, we report on the Hall transport properties of a p-type polycrystalline germanium film, which is grown by the DC magnetron sputtering method. The average grain size of 85 nm is calculated. The resistivity and Hall coefficient of the germanium film were measured at temperatures between 100 K and 350 K. At room temperature (T = 300 K), the resistivity of 1.06 Ω cm, the hole concentration of 7.6 × 1017 cm−3 and mobility of 7.76 cm2V−1s−1 are obtained. The temperature dependence of Hall coefficient presents a steep maximum at a specific temperature (T☆ ≈ 215 K). At the same time, the slope of the log resistivity versus 1/T curve is changed. The unusually results can be well explained by a two-band conduction model, which includes the valence band with a high mobility, and the acceptor impurity band with a much lower mobility. This work gives an evidence for impurity-band conduction in the polycrystalline germanium film.