Experimental observation of a minority electron mobility enhancement in degenerately doped p-type GaAs

The variation of minority electron mobility with doping density in p+-GaAs has been measured with the zero-field time-of-flight technique. The results from a series of nine GaAs films doped between 1 X lOI and 8 X 10” cmm3 show the mobility decreasing from 1950 cm2 V-’ s-l at 1 X 10” cmm3 to 1370 cm2 V-l s-l at 9X 10” cmB3. For the doping range 9 x 1018-8x 1019 cme3, the decreasing trend in mobility is reversed. The measured mobility of 3710 cm2 V-’ s-l at 8 X 10” cmp3 is about three times higher than the measured value at 9 X 1018 cmm3. These results confirm and extend recent transistor-based measurements and are in accord with recent theoretical predictions that attribute the increase in minority electron mobility in p+-GaAs to reductions in plasmon and carrier-carrier scattering at high hole densities.