Polarization-Assisted AlGaN Heterostructure-Based Solar-Blind Ultraviolet MSM Photodetectors With Enhanced Performance

In this work, a high-performance metal–semiconductor–metal solar-blind ultraviolet photodetector (UV PD) based on AlGaN heterostructure (AlGaNH) is fabricated. By utilizing the built-in polarization effect, a highly conductive two-dimensional electron gas channel is induced at the Al $_{{0}.{65}}$ Ga $_{{0}.{35}}\text{N}$ /Al $_{{0}.{4}}$ Ga $_{{0}.{6}}\text{N}$ heterointerface. The AlGaNH PD exhibits a high peak responsivity of 3.42 A/W at 270 nm, which is considerably higher than that of the control AlGaN PD without polarization enhancement. Meanwhile, the device exhibits a low dark current of $1.2\times 10^{-{11}}$ A at 10 V bias, which results in a high photo-to-dark current ratio exceeding $7\times 10^{{3}}$ even when the incident light intensity is as low as $\sim 5 \mu \text{W}$ /cm ² . A theoretical analysis of gain mechanism reveals that the high responsivity can be attributed to the longer lifetime and shorter drift time of the photogenerated carriers within the heterointerface channel. A high specific detectivity can be achieved at elevated temperatures, while a fast response speed can be maintained even at low incident light intensity. This work provides a viable approach to enhance the detection performance of AlGaN-based solar-blind PDs.