Demonstration of AlGaN/GaN-based ultraviolet phototransistor with a record high responsivity over 3.6x107 A/W

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 3.6x10(7) A/W under 265nm illumination and 1.0x10(6) A/W under 365nm 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 (V-GS) dependent photoresponse of the fabricated device with the assistance of band structure analysis. It was found that a more negative V-GS can significantly reduce the rise/decay time for 265nm 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 V-GS has little impact on the switching time for 365nm 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.

Automated summary

This study demonstrates a high-performance ultraviolet phototransistor (UVPT) based on the AlGaN/GaN high-electron mobility transistor (HEMT) configuration, showing superior photodetection performance, especially under 265nm illumination. The gate-bias and band structure analysis play important roles in improving the device's photoresponse, paving the way for next-generation UVPTs.