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 1×1018 and 8×1019 cm−3 show the mobility decreasing from 1950 cm2 V−1 s−1 at 1×1018 cm−3 to 1370 cm2 V−1 s−1 at 9×1018 cm−3. For the doping range 9×1018–8×1019 cm−3, the decreasing trend in mobility is reversed. The measured mobility of 3710 cm2 V−1 s−1 at 8×1019 cm−3 is about three times higher than the measured value at 9×1018 cm−3. 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.