An ultra-wide-bandgap semiconductor photodetector for linear measurement of bright sub-bandgap light

Abstract

Semiconductor photodetectors are conventionally optimized for sensing weak optical signals, and they typically saturate at low-to-moderate light intensity. Here, we demonstrate sub-bandgap AlN photodetectors that exhibit non-saturating linear response to ultra-bright blue light exceeding 40 $\mathrm{W/cm^2}$. The photodetector further shows undistorted linear response at elevated temperature, up to at least 300 $\mathrm{^\circ C}$. This exceptional performance originates from photoresponse mediated by point defects with energy deep in the bandgap ("deep levels") at the metal-AlN Schottky junction. Through dopant design and contact engineering, we demonstrate that a narrow space charge region is essential for enabling ultra-bright light detection and accurate measurement. These results establish a strategy for engineering ultra-wide bandgap (UWBG) semiconductor devices for reliable operation in extreme conditions to meet emerging needs in industrial process control, thermal and nuclear power generation, and aeronautics and spaceflight.