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

Abstract

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0}.{65}}$ </tex-math></inline-formula> Ga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0}.{35}}\text{N}$ </tex-math></inline-formula> /Al <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0}.{4}}$ </tex-math></inline-formula> Ga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{0}.{6}}\text{N}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.2\times 10^{-{11}}$ </tex-math></inline-formula> A at 10 V bias, which results in a high photo-to-dark current ratio exceeding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7\times 10^{{3}}$ </tex-math></inline-formula> even when the incident light intensity is as low as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5 \mu \text{W}$ </tex-math></inline-formula> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . 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.