In this work, we demonstrate a high-performance ultraviolet phototransistor (UVPT) based on the AlGaN/GaN high-electron mobility transistor (HEMT) configuration. When the device is biased at off state, the peak photoresponsivity (R) of 3.6 × 107 A/W under 265 nm illumination and 1.0 × 106 A/W under 365 nm illumination can be obtained. Those two R values are one of the highest among the reported UVPTs at the same detection wavelength under off-state conditions. In addition, we investigate the gate-bias (VGS) dependent photoresponse of the fabricated device with the assistance of band structure analysis. It was found that a more negative VGS can significantly reduce the rise/decay time for 265 nm detection, especially under weak illumination. This can be attributed to a largely enhanced electric field in the absorptive AlGaN barrier that pushes the photo-generated carriers rapidly into the GaN channel. In contrast, the VGS has little impact on the switching time for 365 nm photodetection, since the GaN channel has a larger absorption depth and the entire UVPT simply acts as a photoconductive-type device. In short, the proposed AlGaN/GaN HEMT structure with the superior photodetection performance paves the way for the development of next generation UVPTs.

This letter reports the influence of material quality and device processing on the performance of AlGaN-based Schottky barrier deep ultraviolet photodetectors grown on Si substrates. The thermal annealing can significantly improve Schottky barrier height and wet chemical etching can effectively remove etching damage. Meanwhile, the decrease of threading dislocation density and the pit size, especially the later, can substantially suppress reverse leakage. As a result, the reverse leakage current density of the as-fabricated deep UV photodetector was reduced down to 3×10−8 A/cm2. Furthermore, the responsivity of the deep UV photodetectors was greatly improved by reducing the point defect concentration.

In this article, we report on high-performance deep ultraviolet photodetectors (DUV PDs) fabricated on metal−organic chemical vapor deposition (MOCVD)-grown β-Ga 2 O 3 heteroepitaxy that exhibit stable operation up to 125 °C. The fabricated DUV PDs exhibit self-powered behavior with an ultralow dark current of 1.75 fA and a very high photo-todark-current ratio (PDCR) of the order of 10 5 at zero bias and >10 5 at higher biases of 5 and 10 V, which remains almost constant up to 125 °C. The high responsivity of 6.62 A/W is obtained at 10 V at room temperature (RT) under the weak illumination of 42.86 μW/cm 2 of 260 nm wavelength. The detector shows very low noise equivalent power (NEP) of 5.74 × 10 −14 and 1.03 × 10 −16 W/Hz 1/2 and ultrahigh detectivity of 5.51 × 10 11 and 3.10 × 10 14 Jones at 0 and 5 V, respectively, which shows its high detection sensitivity. The RT UV−visible (260:500 nm) rejection ratios of the order of 10 3 at zero bias and 10 5 at 5 V are obtained. These results demonstrate the potential of Ga 2 O 3 -based DUV PDs for solar-blind detection applications that require high-temperature robustness.

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