A review of the electrical properties of AlxGa1-xN materials for UV photodetector applications

In this paper, recent developments in the electrical characterization and doping of Al x Ga 1-x N will be reviewed. The properties important for the development of solar-blind UV photodetectors will be stressed. For many of the military and commercial applications of UV photodetectors, the photodetectors must be solar-blind with cutoff wavelengths of less than about 280 nm. This means that for devices based on the Al x Ga 1-x N system, the aluminum mole fraction for the active region is nearly 40%. One of the implications for devices is that as the energy gap is increased, doping becomes much more difficult. Therefore, one of the main thrusts of this paper will be the p-type and n-type doping of Al x Ga 1-x N. In addition to the study of the doping of bulk-like Al x Ga 1-x N, the use of Al x Ga 1-x N based superlattices to reduce the dopant ionization energy will be presented. Because GaN is likely to be used for contact layers in solar-blind devices and as an active layer in visible-blind devices, the electrical properties of this better studied binary material will be reported. The role of electrically active defects and unintentional dopants will also be discussed.