Drift mobilities of photocarriers in amorphous hydrogenated GaP made by reactive evaporation

The drift mobilities of photoelectrons and photoholes in a film of a-GaP:H at 300 K were estimated to be 2.3×10 -3 cm 2 /Vs and 1.3×10 -3 cm 2 /Vs, respectively, from a time-of-flight measurement in which the mole ratio of Ga to P, r , in the film was nearly equal to unity. Spectra of the ac photoconductivity for different hydrogenated films with different values of r were measured at 90 K and the results at low photon energies suggest an excitation of electrons and holes at the gap states to the mobility edges of the conduction and valence bands, respectively, owing to the transport of mobile holes as well as mobile electrons deduced from time-of-flight measurements.