Study on photo-induced acoustic charge transport effect in GaN film

In this paper, we investigated transport characteristic of photo-induced carriers by the potential well caused by traveling acoustic wave. We have carried out a basic experiment using delay lines consisting of GaN film on Al₂O₃ substrate. As acoustic waves, we used SAW and guide wave layer mode in GaN thin film and employed MSM detector having the same structure as that of input IDT. The results have shown that the DC output signals is obtained at the output diode for both modes. However, we have observed a relatively complicated phenomenon, such as change on DC output signal polarity depending on the intensity of UV, trapping effect of carriers. We clarified that excess carrier either electron or hole in transported carrier would reasonably explain these effects. We also discuss device structures suitable for UV sensors.