A study of the paramagnetic resonance and transport properties of electrons in gallium phosphide

The work described in this thesis is concerned with the transport properties and paramagnetic resonance of electrons from shallow donor impurities, namely, silicon, sulphur and tellurium, in gallium phosphide (GaP). The crystals of GaP, which had been grown by the epitaxial deposition from the vapour phase, were typically a few square millimeters in area and a hundred microns in thickness. The measurement of the transport properties involved the determination of the conductivity and Hall constant for samples at temperatures in the range 4.2°K to 293°K. From the measurements on samples in the temperature range 100°K to 293°K values of the donor ionization energy and impurity concentrations have been calculated. The temperature dependence of the mobility has been discussed in terms of charge carrier scattering processes. The conductivity and Hall constant for samples at low temperatures (4.2°K to 100°K) have been interpreted in terms of impurity band conduction. The electron paramagnetic resonance (E.P.R.) in n-type GaP has been investigated at frequencies of 10GHz, 35GHz and 70GHz for sample temperatures in the range 2.5°K to 100°K. In each case the E.P.R. spectra consisted of a single broad line and, for samples at 4.2°K, the linewidth was in the range 4.5 to 12.0mT. The g-value of the resonance in GaP containing sulphur and tellurium impurities has been found to be 1.9996(±0.0002). To within the limits of experimental error, this g-value was found to be isotropic and independent of the sample temperature and of the impurity concentration in the sample. For the GaP sample containing silicon impurity the g-value of the resonance was found to be l.9950(±0.0005). The measured g-values have been found to be in approximate agreement with the values calculated from the theory given by Roth. The magnitude and temperature dependence of the linewidth arc discussed in terms of several relaxation processes