| AlGaN/GaN high electron mobility transistors have become a research hotspot at home and abroad due to their high mobility,high breakdown voltage,high temperature resistance and low on-state resistance.GaN double heterojunction HEMT devices are suitable for microwave field due to their excellent domain limiting properties,high breakdown voltage and high reliability.However,the on-state characteristics and back-barrier components show an obvious constraint relationship,and the device blocking capability differs significantly from the theoretical limit,failing to give full play to the advantages of GaN materials with high critical breakdown electric field.To address this problem,this paper introduces the P-doped modulated multi-barrier layer structure into the DHEMT device structure to improve the onstate and breakdown characteristics of the device and reduce the switching losses of the device.Firstly,the progress of domestic and international research on GaN HEMT devices and current research hotspots are summarized.Based on the structural properties of GaN materials,the polarization effect of GaN materials,the mechanism of two-dimensional electron gas formation,and the basic structure and operating principle of GaN double heterojunction HEMT devices are analyzed.The device structure is modelled and characterised using Sentaurus TCAD simulation software,and the effects of different buffer layer A1 components on the device performance are discussed.Secondly,the multi-barrier layer is introduced into the double heterojunction HEMT device structure and its operating mechanism and device transport mechanism are analysed.New quantum potential wells are created between the different A1 component barrier layers due to energy band discontinuities,thus adding two additional conduction channels,and the adjacent AlGaN barrier layers generate polarised charges due to the polarisation effect and the channel carrier concentration is increased.The output characteristics,transfer characteristics,breakdown characteristics,capacitance characteristics,frequency characteristics and switching characteristics of the device are investigated and the device structure parameters are optimised.The results show that the device output characteristics are improved,the on-state resistance is effectively reduced and the switching losses of the device are reduced.Finally,in order to further improve the breakdown voltage of HEMT devices,the P-doped modulation structure is introduced into the GaN dual heterojunction HEMT structure,and the withstand voltage mechanism,electric field distribution and carrier concentration distribution of the device are studied.The new structure,in which the P-type AlGaN buried layer and the N-type AlGaN buffer layer form a PN junction,reduces the peak electric field along the gate edge and introduces a new electric field spike at the interface between the P buried layer and the buffer layer during blocking,resulting in a more uniform electric field distribution and thus an increase in the breakdown voltage of the device.The P-buried layer structure parameters were optimised and analysed.When the buried layer width W=1.5 μm,height H=1.5 μm,distance L=0 μm from the buried layer to the gate edge and the distance D=0.1 μm from the buried layer to the heterojunction,the new structure improved the breakdown characteristics of the device most significantly,increasing the device saturation current by 24.8%,reducing the specific on-state resistance by 14%,reducing the switching losses by 34%,and reducing the input and output capacitance and the switching time is almost unaffected. |
