Backside Etching Thickness Dependence and Reconfigurable Logic Gate Implementation in AlGaN/GaN HEMTs

This work systematically investigates the dependence of AlGaN/GaN high-electron-mobility transistors (HEMTs) on backside etching thickness for ultraviolet (UV) photodetection and explores their potential for reconfigurable logic implementation. By comparing devices with different backside etching depths, including the unetched sample with the Si substrate retained and substrate removed samples etched for 0, 5, and 20 min, we find that moderate thinning (5 min, sample A3) markedly enhances the channel modulation efficiency. Consequently, sample A3 exhibits the strongest photoresponse under both 254 and 365 nm illumination. Under 254 nm illumination, it achieves a peak responsivity (R) of 8.81 × 103 A/W, an external quantum efficiency (EQE) of 4.31 × 106%, and a specific detectivity (D*) of 6.79 × 1013 Jones at an optical power density of 0.1 mW/cm2. The transfer characteristics further exhibit a distinctive two-step rise. Based on the two-dimensional modulation of IDS by VGS and VDS, six types of logic operations, including Inhibit, AND, OR, NAND, NOR, and XNOR, are successfully realized within a single device, demonstrating the feasibility of reconfigurable optoelectronic logic. These findings offer guidance for designing high-performance UV photodetectors and point to a promising pathway toward reconfigurable optoelectronic logic circuits.