Study On The Ingan Back Barrier Hemt Material And High Breakdown Voltage Power Switching

Electricity energy is the most important energy in the world. How to reduceenergy loss in transmission and conversion process is greatly in need. The research ofpower electronics technology is about the delivery, conversion and control of theenergy. Power electronic devices are key components in power electronic systems.AlGaN/GaN HEMT shows the predominant advantage for high performancepower switching because of the high two-dimensional electron gas (2DEG) sheetcarrier density (1E13cm-2) and electron mobility (above1700cm2/Vs at roomtemperature). GaN devices have100times lower specific on-resistance than Si, and50times than SiC, theoretically.This dissertation focuses on high breakdown voltageAlGaN/GaN HEMT for low-loss, high speed power switching application. The mainachievements are summarized as following:1. Design and grown of AlGaN/AlN/GaN/InGaN/GaN DH-HEMT materialThe conduction band profile of the AlGaN/AlN/GaN/InGaN/GaN DH-HEMTand conventional AlGaN/AlN/GaN HEMT are calculated by self-consistentSchr dinger-Poisson algorithms. The InGaN back barrier layer significantly improvesthe electron confinement in the channel by introducing a conduction banddiscontinuity at the channel/buffer interface.There are almost no electrons in the GaNbuffer layer in the DH-HEMT compare with the conventional HEMT. The2DEG inthe minor channel is about3‰of the total2DEG in the DH-HEMT in the simulation.The electrons in the minor channel are not confined well and can easily spill over tothe major channel because of low In composition InGaN interlayer.The low temperature GaN spacer layer is grown to protect the InGaN backbarrier interlayer, RBS results shows that the low temperature GaN spacer layerprotects the InGaN back barrier interlayer well. So, the GaN channel layer can begrown at1070°C. The In composition is determined to be5%by DC-XRD and RBSmeasurements. Hall measurements show that the mobility is9253cm2/Vs at4.3K,1552cm2/Vs at room temperature, higher than similar structure reported. The C-V testreveals no additional conductive channel, agree with the simulation results. The sheetresistance is399Ω/□, with wafer uniformity1.9%, which is favorable for large-size devices and improving yield.2. Fabrication of AlGaN/AlN/GaN/InGaN/GaN DH-HEMT devicesHigh voltage switch devices are fabricated using AlGaN/AlN/GaN/InGaN/GaNDH-HEMT material. A maximum drain current density of380mA/mm is observedunder Vgsof0V and a transconductance (gmax) of108mS/mm is obtained with adrain-source voltage of2V. The breakdown voltage is640V under Vgsof-6V.