Persistent Photoconductivity Study In Algan Superlattice

The transport properties of GaN and its alloys are attracting increasing interest due to the potential application of these materials for solar blind photodetectors and high mobility transistors. Because of the large band gap, the applications of AlxGa1-xN are extensive, such as for visible-blind ultraviolet detectors, laser diodes, and short-wave light emitting diodes (LEDs). However, the persistent photoconductivity (PPC) of GaN based photoconductive devices affects its applications. In order to study the origin of PPC, we designed solar blind ultraviolet photoconductive detector, which consists of n-Al0.65Ga0.35N top contact layer (100nm), n-Al0.42Ga0.58N/i-Al0.65Ga0.35N superlattice layers (200nm), i-Al0.65Ga0.35N layer (600nm), AlN buffer layer and double polished sapphire substrate. Moreover, there are photoconductive devices with different photosensitive areas. Investigations of electric-field effects and thermal effects on PPC in n-Al0.42Ga0.58N/i-Al0.65Ga0.35N superlattice are presented. We have observed that, by applying a high-voltage pulse, the course of PPC was effectively accelerated: With the same pulse width and different voltage, in the appropriate range, the higher of the voltage, the course of PPC was more effectively accelerated; with the same voltage and different pulse width, in the appropriate range, the wider of the pulse width, the course of PPC was more effectively accelerated. And PPC effect strongly depends on the temperature. The decay time of the PPC depend on the temperature and become longer with a decreasing temperature.