Physical insights into trapping effects on vertical GaN-on-Si trench MOSFETs from TCAD

Vertical GaN power MOSFET is a novel technology that offers great potential for power switching applications. Being still in an early development phase, vertical GaN devices are yet to be fully optimized and require careful studies to foster their development. In this work, we report on the physical insights into device performance improvements obtained during the development of vertical GaN-on-Si trench MOSFETs (TMOS’s) provided by TCAD simulations, enhancing the dependability of the adopted process optimization approaches. Specifically, two different TMOS devices are compared in terms of transfer-curve hysteresis (H) and subthreshold slope (SS), showing a ≈ 75% H reduction along with a ≈ 30% SS decrease. Simulations allow attributing the achieved improvements to a decrease in the border and interface traps, respectively. A sensitivity analysis is also carried out, allowing to quantify the additional trap density reduction required to minimize both figures of merit.