Temperature-dependent Hall study on p-type GaN epilayers grown by metal-organic chemical vapor deposition

Temperature-dependent Hall measurements were performed on p-type GaN epilayers grown on (0001) sapphire substrates by metal-organic chemical vapor deposition in the temperature range of 100 K to 500 K. The resistivity, hole concentration and hole mobility were monitored as a function of temperature. By analyzing the temperature dependence of these electrical properties, the activation energies of 156 meV and 149 meV were obtained for the relatively low p-conductive samples and highly p-conductive samples, respectively. Also conduction mechanisms were found to be free carrier conductions contributed from Mg acceptors for relatively low p-conductive samples (p=3x 10(17)cm(-3) at room temperature) at all temperatures and for highly p-conductive samples (p=1.2x10(18)cm(-3) at room temperature) at high temperature. At low temperature, impurity-band conduction must also be involved when doping concentration is high. Finally scattering factors limiting hole mobility were discerned at different temperatures.