Study On A New Structure Of GaN-based Power Electronic Devices

Wide band gap semiconductor materials represented by GaN?Gallium Ntride?have great advantages in the field of power semiconductor devices and are promising to replace silicon materials due to its unique properties such as wide bandgap?³.4eV?,high critical electric field?³.3×10⁶V/cm?,high saturated electron velocity?².7×10⁷cm/s?and high thermal conductivity?²W/cm·K?.Power field effect transistors are core electronic devices in power electronic systems.It is of great value to develop a vertical GaN power transistor with reverse conduction capability,high off-state blocking voltage,low on-resistance and high switching speed.A high performance GaN power transistor with reverse conduction capability is proposed in the paper and the main contents are as follows:?1?A split gate vertical GaN power transistor with reverse conduction capability abbreviated as RCVFET is proposed in the paper and it has following characteristics:1,We adopted the p-type GaN as the gate and the AlGaN barrier recess below the gate is introduced to modulate the threshold voltage.Aided by the Sentaurus-TCAD software,we showed that the threshold voltage will be varied with various recess thicknesses,ranging from 0.7V to 2.1V.2,Unlike the traditional lateral P type GaN-gated HEMT,reverse conduction path in the RCVFET is separated from the forward conduction path and the reverse current is conducted across Schottky junction which lead to the dramatic decrease of the turn-on voltage.Compared with vertical P type GaN-gated HEMT in which the reverse current is conducted across the body PN junction,the device features a lower reverse turn-on voltage and a short reverse recovery time.3,The Schottky source is located between dual gates.The gate area of RCVFET is dramatically decreased and Q_GD is reduced to 25%of that obtained from single gate devices.4,The electric field originally pointed towards the Schottky source is mainly screened by the P base,leading to the suppression of the leakage current created by the Schottky junction in the off-state blocking mode.The breakdown voltage of the RCVFET is 1800V and the specific on-resistance is 0.98m?·cm² when the width of the JFET region(L_JFET)and the length of the field plate(L_FP)is 5.0?m and 1.0?m respectively.?2?According to the outcome of Sentaurus-TCAD,crucial parameters such as L_JFET,L_SS and contact resistance between the source and P base region will be discussed for the performance of the device and the hole injection effect caused by parasitic bipolar transistor will be depressed.The reverse recovery time and gate charge of the device are simulated in mixed-mode simulation.A DC-DC 800V to 380V buck converter model will be constructed in order to characterize the switching speed and switching losses and the comparision between RCVFET and CVFET will be made.