Research On The Influence Of Substrate Thermal Boundary Resistance On The Thermal Distribution Of AlGaN/GaN HEMT Devices

As one of the representative materials of the third-generation wide-bandgap semiconductor,gallium nitride material has excellent characteristics such as high thermal conductivity,high breakdown field strength,and high electron mobility.GaN-based HEMTs are widely used under fileds with high temperature,high pressure and high power,such as radar and 5G communications.However,the temperataure rise of the device is significant due to its selfheating effects under high power circustances,which may cause the device’s degradation,failure and shortened life.In order to overcome the problems caused by the thermal instability of GaN-based HEMT devices,scholars have conducted in-depth researches on the thermal issues of GaN HEMTs,and found that the thermal boundary resistance(TBR)between GaN and the substrate material may significantly improve the device channel junction temperature.Therefore,this paper deeply shows the influence of the boundary thermal resistance of different substrates on AlGaN/GaN HEMT devices,and through this research,we understand the factors that affect the channel junction temperature of AlGaN/GaN HEMT devices,and put up some optimization schemes of the thermal design and management of the device.At first,this paper uses COMSOL software to conduct two-dimensional modeling and simulation of AlGaN/GaN HEMT devices,and analyzes the influence of substrate material,boundary thermal resistance,gate length and gate-drain distance on the channel junction temperature of AlGaN/GaN HEMT devices,and obtains the channel temperature distribution of the device and the longitudinal temperature map at the GaN-substrate junction.The result shows that diamond has the best heat dissipation effect,followed by SiC,and Si is the worst.With the increase of power density,the rise rate of the channel junction temperature will increase,and the increase in channel junction temperature of AlGaN/GaN HEMT devices is linearly related with the TBR,and the device with substrate of high thermal conductivity are more easily affected by TBR,and TBR affects the overall temperature distribution and channel junction temperature of the AlGaN/GaN HEMT device mainly by affecting the temperature distribution of the GaN buffer layer,which is also called the active area of the device;the increase in the gate length and gate-drain distance will reduce the channel junction temperature,and makes it that the temperature difference of the overall device is relatively smooth,which improves the thermal reliability of the device.Secondly,a three-dimensional finite element simulation model of the multi-gate AlGaN/GaN HEMT device was established.The simplified heat propagation model was used to guide and analyze the factors that affect the heat distribution of the device,and some optimization of the three-dimensional models were performed on the basis of the twodimensional model.The influence of substrate material,TBR and gate finger spacing on the thermal distribution of multi-gate finger AlGaN/GaN HEMT devices is analyzed,which obtains the detailed temperature distribution diagrams of the entire device and the channel.The results show that under high power density,the self-heating effect of the device with Si substrate is the worst,resulting in the obvious temperature rise.SiC and diamond have good heat dissipation under high power;the channel junction temperature of multi-gate finger devices increases with the increase of TBR,but the increase rate has an upper limit,which probably because that the heat dissipation effect of high-power devices mainly depends on the heat sink layer;increasing the distance between the gate fingers will reduce the thermal coupling effect between the gate fingers and effectively reduce the channel junction temperature.Finally,through the simulation analysis of the two AlGaN/GaN HEMT device structures,some suggestions for the thermal optimization of AlGaN/GaN HEMT devices are put forward: Under the premise of not affecting the output characteristics of the device,use high thermal conductivity substrate materials and select high heat The conductive nucleation layer reduces the boundary thermal resistance of the GaN-substrate,appropriately increases the gate length,and increases the gate-to-drain spacing and gate-finger spacing to reduce the channel junction temperature of the AlGaN/GaN HEMT device and improve the thermal stability of the device.