The Study Of The Gate Drain Region Of AlGaN/GaN HEMT Devices On Electrical Performance

GaN is a typical representative of the third generation of wide bandgap semiconductor materials.It has excellent properties such as large band gap,high critical breakdown electric field,high electron saturation speed,high temperature resistance and radiation resistance.And a very high concentration of two-dimensional electron gas(2DEG)will be produced at the AlGaN/GaN heterojunction interface,while a 2DEG with high electron mobility will form a conductive channel under the interface.So it has broad application prospects in the fields of high frequency,high power,and microwave.Although AlGaN/GaN HEMT devices have attracted a lot of attention in the academic field as a hot spot,the breakdown voltage of GaN HEMT is still far below the theoretical breakdown limit of GaN materials.Therefore,the focus of this paper is to use the Sentaurus TCAD simulation software to design and simulate new device models,optimize device structure and parameters,and improve the breakdown voltage of the device.The main research contents are:(1)An AlGaN/GaN high electron mobility transistor(DCBL-HEMT)with a double charge region barrier layer structure is proposed.First,the structure and operation of two negative charge regions in the barrier layer between the gate and the drain are described.The introduction of its negative charge can be realized by fluorine plasma treatment.Compared with the transistor of the ordinary passivation layer structure and the field plate structure,electrons in the channel of the transistor with the double charge region barrier layer structure are depleted by negative charges in the barrier layer.As far as possible,the electric field concentration at the edge of the gate is improved.And the electric field distribution is more uniform.The electric field distribution in the channel layer is adjusted.And the breakdown voltage of the device is effectively improved.Then,optimize the length,concentration,and distance of the charge region by simulation by controlling the variable.And a HEMT device with a breakdown voltage of 284 V is obtained.(2)A novel AlGaN/GaN high electron mobility transistor(SGF-HEMT)with a stepped AlGaN layer was proposed and its mechanism was studied.In this work,the effects of different thicknesses and lengths of the stepped AlGaN layer on the 2DEG,electric field and breakdown voltage of the device were calculated by simulation.It was found that the HEMT device with the stepped AlGaN layer structure not only produceda new electric field peak between the edge of the layer and the edge of the gate field plate,and also the electric field peak near the edge of the gate is reduced,resulting in a higher breakdown voltage,resulting in a HEMT device with a breakdown voltage of641 V.(3)Based on the research of SGF-HEMT device,the addition of fluoride ions in the lower barrier layer depletes the two-dimensional electron gas in the channel layer,which improves the electric field distribution of the lower channel layer.The effect of implanting fluoride ions under the SGF-HEMT gate on the electrical properties of the device was calculated and analyzed,such as electron density,potential distribution,threshold voltage,breakdown voltage,output current,and on-state resistance.An enhanced HEMT device with a breakdown voltage of 1113 V was obtained.