Minority electron mobility in a p-n GaN photodetector

Photoconductive transients and responsivity in a GaN p-n UV photodetector under different applied voltages are investigated at room temperature. The electron mobility of minority carriers in the p-GaN epilayer has been measured by a diffusion time-of-flight technique, and was found to be about 0.12 cm(2) V-1 s(-1) with the bias between 1 V and 12 V. The difference of the electron mobilities between the minority carriers in p-GaN and the majority carriers in n-GaN is explained by different scattering mechanisms. The neutral impurity and phonon scattering mechanisms dominate the minority electron mobility in p-GaN. The photoconductive responsivity increases nearly linearly at low voltage and saturates at about 10 V, corresponding to a saturation field of approximately 3.7 x 10(4) V cm(-1). The implication of these results for applications of GaN UV detectors is also discussed.