High-Performance p-GaN/AlGaN/GaN HEMT-Based Ultraviolet Phototransistors With fW-Level Weak Light Detection Capacity

Abstract

In this work, high-performance ultraviolet (UV) phototransistors (PTs) based on the p-GaN/ AlGaN/GaN HEMT structure were reported. An innovative strategy making a tradeoff between the absorption thickness of the incident light and the retraction distance of the depletion region was developed for the first time. The optimal PTs exhibited a large photo-to-dark-current ratio (PDCR) of $1.30\times 10^{{11}}$ , a high responsivity of $5.50\times 10^{{5}}$ A/W, and a record-high UV-to-visible rejection ratio (UVRR) over $1\times 10^{{9}}$ while maintaining a fast response time of $136.0~\mu $ s. Moreover, the devices present excellent weak light detection capability with a threshold light intensity as low as 7.90 nW/cm ² , enabling direct detection of the 119.05 fW signal. Additionally, the measurement of the noise characteristics revealed that the low-frequency noise of the device originating from the trap dominated 1/f flicker noise, and a superior detectivity ( ${D}^{\ast }\text {)}$ above $1\times 10^{{18}}$ cm $\cdot $ Hz $^{\text {1/ {2}}}$ /W was achieved. The results suggest the enormous potential of p-GaN-based UV PTs for high-sensitivity visible-blind UV detection.