Optimization of interface electrostatics in T-gate GaN HEMTs for advanced pH sensing applications

Abstract

This work investigates a novel T-gate AlGaN/AlN/GaN HEMT designed as a pH sensor by incorporating electrolyte solution in the cavities on both sides of the gate. The sensor’s performance is evaluated based on the variation in the interface charge density corresponding to the change in electrolyte solution pH. This study examines the impact of varying pH solutions on the device’s characteristics, specifically focusing on threshold voltage sensitivity and drain current sensitivity. Furthermore, the gate voltage was optimized to achieve maximum transconductance (g_m) and, consequently, the highest sensitivity to pH changes. The linearity of the device was evaluated using VIP2, VIP3, IIP3, and IMD3 analyses. Notably, the proposed sensor exhibits an average threshold voltage sensitivity of 180 mV/pH, significantly exceeding the Nernstian limit (59 mV/pH), alongside a current sensitivity of 70.21 mA/mm.pH. These results underscore the potential of this recessed T-gate AlGaN/AlN/GaN HEMT as a compelling alternative for advanced pH sensing applications.