Photodetectors for the ultraviolet (UV) range of the electromagnetic spectrum are in great demand for several technologies, but require the development of novel device structures and materials. Here we report on the high detectivity of UV photodetectors based on well-ordered laterally mesoporous GaN. The specific detectivity of our devices under UV-illumination reaches values of up to 5.3 × 10 Jones. We attribute this high specific detectivity to the properties of the mesoporous GaN/metal contact interface: the trapping of photo-generated holes at the interface lowers the Schottky barrier height thus causing a large internal gain. High detectivity along with a simple fabrication process endows these laterally mesoporous GaN photodetectors with great potential for applications that require selective detection of weak optical signals in the UV range.

On the basis of the laterally porous GaN, we designed and fabricated a composite porous GaN structure with both well-ordered lateral and vertical holes. Compared to the plane GaN, the composite porous GaN structure with the combination of the vertical holes can help to reduce UV reflectance and increase the saturation photocurrent during water splitting by a factor of ∼4.5. Furthermore, we investigated the underlying mechanism for the enhancement of the water splitting performance using a finite-difference time-domain method. The results show that the well-ordered vertical holes can not only help to open the embedded pore channels to the electrolyte at both sides and reduce the migration distance of the gas bubbles during the water splitting reactions but also help to modulate the light field. Using this composite porous GaN structure, most of the incident light can be modulated and trapped into the nanoholes, and thus the electric fields localized in the lateral pores can increase dramatically as a result of the strong optical coupling. Our findings pave a new way to develop GaN photoelectrodes for highly efficient solar water splitting.