The Mobility and Life of Injected Holes and Electrons in Germanium

The mobilities of holes injected into $n$-type germanium and of electrons injected into $p$-type germanium have been determined by measuring transit times between emitter and collector in single crystal rods. Strong electric fields in addition to those due to injected current were employed so that spreading effects due to diffusion were reduced. The mobilities at 300°K are 1700 ${\mathrm{cm}}^2$/volt-sec for holes and 3600 ${\mathrm{cm}}^2$/volt-sec for electrons with an error of probably less than five percent. The value for electrons is about 20 percent higher than the best estimates obtained from the conventional interpretation of the Hall effect and the difference may be due to curved energy band surfaces in the Brillouin zone. Studies of rates of decay indicate that recombination of holes and electrons takes place largely on the surface of small samples with constants varying from ${10}^2$ to > ${10}^4$ cm/sec for special treatments.