On the hole effective mass and the free hole statistics in wurtzite GaN

We study the influences of band splitting and band anisotropy on the statistics of free holes and on the electrical transport in p-type GaN. Published experimental results for the hole effective mass span a wide range, m h = 0.3–2.2 m o . Based on theoretical data, we determine reliable values for the pertinent effective masses. We also examine the distribution of free holes among three closely spaced valence bands. Around room temperature, the density-of-states effective mass is calculated to be m h3ds = 1.25 m o . Depending on the direction of electrical current, the roles of different valence bands are distinctive. The holes from the A-band prevail in the transversal direction. However, the holes from the C-band dominate the transport along the c -direction, although their relative concentration is the smallest. This effect could play a role in optoelectronic devices.