Theoretical studies on hole transport and the effective hall factor in cubic phase of p-type GaN

The theoretical hole transport characteristics (Hall and drift mobilities, and effective Hall factor) are reported for the cubic phase of p-typc GaN. These characteristics are calculated using the "relaxation time approximation" as a function of temperature. The calculations show that the dominant lattice scattering mechanism for holes is the acoustic deformation potential. In the calculation of the scattering rate for ionized impurity mechanism, the activation energy of 120 or 250 meV is used at different compensation ratios of given acceptor concentrations. Comparing the scattering time in these activation energies, it is found that the activation energy difference is negligible at high compensation ratios. We determined the anisotropy factors separately, due to the anisotropy of the energy surface for heavy- and light-hole bands, and these parameters arc taken into account in the Hall factor calculations. The Hall factors are very important when we attempt to compare the calculated drift mobility with measured Hall ones. The theoretical Hall mobilities at total hole concentrations of 3.5 × 10¹⁵ and 3.5 × 10¹⁶ cm^-3 are about 312 and 225cm²V^-1s^-1, respectively, with the activation energy of 120 meV and the compensation ratio of 0.5 at 300 K. It is found that Hall mobilities are strongly affected by the compensation ratios. The obtained effective Hall factor in the cubic phase of GaN is in the range of 1.4 (T = 120K) to 1.8 (T = 400 K).