Band-Edge Potentials of n-Type and p-Type GaN

The band-edge potentials of p-GaN in aqueous solutions were examined with photocurrent measurements, and those of n-GaN were examined in both photocurrent measurements and impedance spectroscopy. The measured band-edge potentials were different for both the different materials and the different measurement techniques. These differences are attributed to differences in the interface charging due to slow charge-transfer kinetics at the interface between the semiconductor and the solution. Using photocurrent measurements, the conduction band-edge potential was Φ_c,s = (-1.092 - 0.063 × pH) V vs. a standard calomel electrode (SCE) for p-GaN and Φ_c,s = (-0.538 - 0.046 × pH) V SCE for n-GaN. Using impedance spectroscopy, the conduction band-edge potential for n-GaN was Φ_c,s = (-0.816 - 0.047 × pH) V SCE.