Temperature-dependent hole transport in GaN

The transport properties of Mg-doped, p-type GaN films. grown by MOCVD have been measured using Hall effect and resistivity measurements over a temperature range of 400-120 K. The mobility is found to increase slowly over the temperature range of 400-150 K. Below this temperature the mobility is seen to decrease rapidly, while the corresponding Hall carrier density goes through a minimum before increasing to lower temperatures. These results have been analysed, using a two-band model. This incorporates a simple valence band model, calculated using a relaxation time approximation, and additional transport within an acceptor impurity band. A good fit has been obtained self-consistently to both the mobility and carrier density over a temperature range of 400-120 K. We find that neutral scattering plays an important role in limiting the hole mobility.