High Voltage Structural Design And Simulation Study Of AlGaN/GaN HEMT Devices

Gallium nitride(GaN)materials have excellent characteristics such as wide forbidden band,high critical breakdown field strength,high saturation electron velocity,high corrosion resistance,and high temperature resistance,making them the leading third-generation semiconductor materials.Using the spontaneous polarization and piezoelectric polarization effects of GaN and aluminum gallium-nitride(AlGaN)heterojunctions to generate high concentration and high density of two-dimensional electron gas(2DEG)can realize high electron mobility transistor(HEMT)devices with high operating frequency and excellent voltage resistance.However,due to the device structure design and other reasons make conventional AlGaN/GaN HEMT devices in the cutoff state,the electric field is mainly concentrated at the gate,resulting in the breakdown phenomenon inside the device under the action of high electric field.The breakdown voltage and GaN material theoretical limit is still a small gap,GaN HEMT power device breakdown voltage there is still a lot of room for improvement.To address this situation,this paper investigates the following aspects.(1)In order to have a more detailed and profound understanding of AlGaN/GaN HEMT devices,the AlGaN barrier layer that affects the two-dimensional electron gas concentration is investigated,mainly from the Al component of the AlGaN barrier layer and the thickness of the AlGaN barrier layer on the forward characteristics of the device.(2)An AlGaN/GaN HEMT device structure with uniform notch barrier is proposed.The structure presents a uniformly distributed slotted AlGaN barrier layer between the gate and drain,and the concentration of two-dimensional electron gas in the channel corresponding to the slotted AlGaN barrier layer decreases to form a low-concentration two-dimensional electron gas region,which is very favorable for the expansion of the auxiliary depletion region.The introduced notches create many electric field peaks,which enhance the average electric field strength on the device surface,thus improving the device's voltage resistance.Simulation results show that the breakdown voltage of 821V is improved by 215%compared with conventional AlGaN/GaN HEMT devices based on the optimal parameters of the device,and the on-state resistance Ron,sp is increased by only 0.14 m?·cm~2.(3)An AlGaN/GaN HEMT device structure with a partial P-GaN buried layer is proposed.This structure introduces a partial P-GaN buried layer in the GaN buffer layer according to the RESURF principle,and uses P-type doping to form a PN junction with the channel electrons to increase the buffer layer conduction band.The free carriers in the channel are accelerated by the strong electric field and their ability to break free from the potential well is reduced,thus suppressing the buffer layer leakage current.At the same time,multiple new peak electric fields are formed in the drift region of the device to improve the average electric field of the device.Simulation results show that the breakdown voltage of 410 V is improved by 193% compared with conventional Al Ga N/Ga N HEMT devices based on parameter optimization,and the on-state resistance Ron,sp is increased by only 0.02m?·cm~2.