TEMPERATURE-DEPENDENCE OF THE ELECTRON-MOBILITY IN THE DELTA-1C MINIMA OF GERMANIUM

At high pressures the band structure of germanium becomes similar to that of silicon at atmospheric pressure, making the Delta 1c minima accessible to direct electrical investigation. Measurements of the electron mobility are reported; it was found to vary from 800 cm2 V -1 s-1 at 300K to 6400 cm2 V-1 s-1 at 120K, corresponding to a temperature dependence of T -2.7. Analysis, assuming effective mass ratios mt*= 0.288, m1*=1.353 and an acoustic deformation potential of 3.61 eV, gave intervalley coupling constants of 3.7*108 and 2.9*108 eV cm-1 for the 430K LO and the 320K LA phonons respectively. A negligible coupling constant was found for the low-energy LA phonon, as was also determined for silicon and GaP.