Ultraviolet photonic response of AlGaN/GaN high electron mobility transistor-based sensor with hydrothermal ZnO nanostructures

We present the first active high-performance ultraviolet (UV) sensor based on aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) with zinc oxide (ZnO) nanorods (NRs) selectively grown on the gate area by hydrothermal method. Faster response and recovery times (∼10 and ∼190 ms) are obtained from the NR-gated sensors than those (∼270 and ∼660 ms) of the seed-layer-gated devices by the periodic switching of the UV light under the same measurement conditions. This response speed is much superior to those of other ZnO nanostructure-based passive sensors, which exhibit much slower response times of several tens or hundreds of seconds. The NR-gated HEMT sensors show a very high responsivity of 1.1 × 10⁵ A/W at a source optical power of 100 W and a wavelength of 300 nm, which is about one order higher than the best responsivity of a ZnO nanowire-based sensor reported to date. This improvement in responsivity and sensing speed is owing to the reduction in dimensionality with the ultra-high surface-to-volume ratio of the three-dimensional ZnO NR sensing structure and high performance characteristics of the AlGaN/GaN HEMTs.