Electron Mobility and Impurity Concentration in<i>n</i>-GaP Crystals Grown by Slow Cooling of Ga Solution

Abstract

n-GaP crystals were grown by slow cooling of Ga solution doped with various concentrations of Te. Electron mobility and carrier concentration in the crystals were measured in the temperature range from 77°K to 400°K. The analysis of mobility showed that the dominant process limiting the electron mobility is the intervalley scattering at 200–400°K and the scattering by space charge regions at 77–200°K. As for the intervalley scattering, the LA phonon near the X point, Tc=300°K, appeared to make a dominant contribution. The coupling constant for this phonon was estimated to be 0.7×109 eV/cm, just the same as the effective coupling constant for the dominant intervalley phonon in Si. The inhomogeneity in the crystals and the dependence of carrier concentration on doping level were also investigated and compared with those in the crystals grown by thermal gradient method and by vapor-phase epitaxy.