The anisotropy of GaN(11-20) makes it possible to fabricate polarized ultraviolet (UV) photodetectors (PDs) for applications in fields such as remote sensing and airborne astronomical navigation. The defect density has a significant effect on the performance of GaN(11-20)-based UV PDs. However, the mechanism through which different defects and their densities affect the performance of these devices is unclear. Therefore, in this work, we investigated the mechanisms of the screw or mixed dislocation, edge dislocation, and basal stacking fault (BSF) densities affecting the dark current, responsivity, and response time of GaN (11-20)-based PDs, respectively. We observed that the screw or mixed dislocation increased the dark current mainly through reducing the Schottky barrier height and forming leakage current, whereas the edge dislocation and BSF decreased the responsivity by reducing the electron mobility. Furthermore, all the three types of defects increased the response time through forming traps to recombine the holes with electrons and thus delaying the escape of carriers. These results are highly significant for developing nonpolar GaN-based UV PDs.

As compared with their bulk materials, III-nitride nanosheets, including gallium nitride, aluminium nitride, indium nitride, reveal wider bandgap, enhanced optical properties, anomalously temperature-dependent thermal conductivity, etc, which are more suitable for the fabrication of nano-photodetectors, nano-field electron transistors, etc, for the application in the fields of nano-optoelectronics and nano-electronics. Although the properties of III-nitrides have been predicted based on the first-principles calculation, the experimental realization of III-nitride nanosheets has been restricted primarily due to dangling bonds on the surface and strong built-in electrostatic field caused by wurtzite/zinc-blende structures. To tackle these issues, several effective approaches have been introduced, and the distinct progress has been achieved during the past decade. In this review, the simulation and prediction of properties of III-nitride nanosheets are outlined, and the corresponding solutions and novel developed techniques for realisation of III-nitride nanosheets and defect control are discussed in depth. Furthermore, the corresponding devices based on the as-grown III-nitride nanosheets are introduced accordingly. Moreover, perspectives toward the further development of III-nitrides nanosheets and devices are also discussed.

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