Electrical transport properties of highly Mg-doped GaN epilayers grown by MOCVD

In a temperature range of 750-1050 °C rapid thermal annealing was carried out to activate Mg impurities in GaN epilayers grown on sapphire by metalorganic chemical vapor deposition. Activation increased with temperature until near 950 °C, and then decreased very slowly with further increasing temperatures. Hall mobility decreased (from 16.5 cm²/V s at 750 °C) with increasing annealing temperature until near 1000 °C (12.8 cm²/V s). The temperature-dependent Hall effects demonstrated very low compensation, around 1%, for all the samples. The low compensation and high mobility may be due to post-growth cooling in nitrogen atmosphere.