Semiconducting Properties ofMg2Ge Single Crystals

Single crystals of ${\mathrm{Mg}}_2$Ge have been obtained from melts of the constituents, and Hall effect and electrical resistivity measurements have been made from 77°K to 1000°K. Undoped crystals were $n$-type and had saturated impurity carrier concentration as low as 3×${10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$; silver-doped crystals were $p$-type and had saturated impurity carrier concentrations roughly proportional to the amount of added silver. The room-temperature Hall mobilities were observed to be 280 ${\mathrm{cm}}^2$/volt-sec for electrons and 110 ${\mathrm{cm}}^2$/volt-sec for holes. The hole mobility observed in the extrinsic region (120°K to 350°K) of the highest purity $p$-type sample and the mobility difference observed in the intrinsic region (350°K to 700°K) of the $n$-type samples varied with temperature as $T^{-2.0\mathrm{}}$. The mobility difference was found to decrease faster than $T^{2.0}$ above 700°K. The width of the energy gap at absolute zero, as determined from the temperature dependence of both the resistivity and the Hall effect in the intrinsic region, was 0.69±0.01 ev.