An Investigation of Temperature Dependence of Electrical Properties in Ion-Implanted Gallium Arsenide.

Four samples of GaAs:Mg (p-type) with ion-implanted doses of 5 x 1012 , 1 X 1013, 3 X 1013 and 1 x 1014 ions cm- 2 were investigated for their temperature dependent electrical properties. The resistivity and Hall constant for each sample were determined directly by the van der Pauw technique. The measurements were made from room temperature to liquid helium temperature. Sheet carrier (hole) concentration, N. and carrier mobility were then calculated for each sample as a function of temperature. The experimental data points in the linear region of the In(N.) vs l/T curve were selected to achieve a computer fit to the theoretical expression for the hole concentration. Optimized values for acceptor and donor concentration, as well as impurity ionization energy were determined. Using these optimized values, the sheet carrier concentration was calculated and plotted vs l/T. The deviation between the experimental and theoretical curves at low temperatures is believed to be due to impuriy band and hopping conduction. The plot of resistivity as a function of temperature indicates impurity band and hopping conduction at low temperatures. The impurity activation energy calculated from this curve was found to be in good agreement with the optimized ionization energy. The mobilities due to polar optical phonon scattering, piezoelectric acoustic phonon scattering, deformation potential acoustic phonon scattering, neutral impurity scattering, and ionized impurity scattering, as well as effective mobility were calculated and compared with experimental values. Good agreement was found at low doses (5 X 1012 cm- 2 ), but generally decreasing agreement was found at higher doses. The discrepancies were attributed to the presence of impurity band and hopping conduction mechanisms