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.