Effect of Barrier Layer Thickness on the Sensing Performance in AlGaN/GaN HEMT-Based Bio-Sensors

This study investigates the impact of AlGaN barrier layer thickness (15–30 nm) on the sensitivity of AlGaN/GaN HEMT sensors for uric acid detection using Sentaurus TCAD simulations. Device behaviour has been analysed with and without surface-bound uric acid (UA) charge. At a uric acid concentration of 55 μM, the threshold voltage sensitivity increases with AlGaN barrier thickness, reaching a maximum of 0.572 mV/μM at 28 nm, while the drain current sensitivity shows an inverse trend, with the highest value of 62.8 μA/μM observed at 15 nm. A thickness range of 20–28 nm offers the best balance between both sensitivities, providing guidance for optimizing HEMT-based biosensors. Therefore, this study demonstrates that the AlGaN barrier thickness plays a crucial role in sensitivity, as it affects the two-dimensional electron gas (2DEG) concentration at the AlGaN/GaN interface, which in turn directly influences the device’s response to surface charges.