3-D Simulation Study of a Normally-OFF GaN Lateral Multi-Channel JFET With Optimized Electrical Field Transfer Terminal Structure

In this work, a lateral multichannel GaN-based junction field effect transistor (JFET) is proposed and studied by 3-D numerical simulation to realize normally- OFF operation and retain large output current simultaneously. Normally- OFF operation can be realized more easily due to the use of double side p-n junction gate for every single channel. We calculate the variations of the maximum saturation current and threshold voltage with channel thickness and doping concentration and obtain the corresponding transition chart from normally- ON to normally- OFF operation. Based on these optimized structure parameters, we further attempt electrical field transfer terminal technologies to improve the breakdown characteristics for the device, and we find that the drain field plate technology has much better effect than the reduced surface field technology, such that the drain field plate can transfer high electric field from the drain terminal into the insulation dielectric. The simulated breakdown voltage of the designed JFET with drain field plate reaches 880 V, leading to an increase by 50% compared to that without drain field plate. In addition, the designed device shows a relatively high cutoff frequency up to gigahertz.