Thermal Characteristics And Reliability Analysis Of GaN Based HEMT

Gallium nitride materials are much better than the first two generation semiconductor materials in terms of bandgap width,breakdown electric field intensity,thermal conductivity and electron saturation drift speed.Therefore,it has great potential in the field of high temperature,high frequency and high power.But the AlGaN/GaN HEMT device working under the above conditions will produce a significant self heat effect.This effect will have a bad effect on the performance of the device,so it is very important to reduce the working temperature of the device and to reduce the self heat effect.In addition,the subthreshold characteristics of the device also have a great influence on the reliability of the device.It is of great significance for the development and application of AlGaN/GaN HEMT by optimizing the structure of the device and improving the performance of the device.In this thesis,the works are based on the Silvaco Atlas platform.The thermal characteristics and reliability of AlGaN/GaN HEMT devices are simulated.By changing the parameters and structure of the device,some effective ways to improve the performance of the device are searched.The main works of this thesis are as follows:(1)The influence of field plate structure on the distribution of temperature field of AlGaN/GaN HEMT is simulated,and the possible factors affecting the temperature field distribution of the field plate structure are analyzed.After adding gate field plate and source field plate structure,the two-dimensional electron gas concentration in the channel decreases and the electric field distribution changes.There is a new temperature peak at the edge of each field plate.The channel peak temperature at the edge of the drain side gate is reduced,and this reduction increase as the number of gate field plates increases.The simulation results show that the field plate structure influences the temperature distribution in the AlGaN/GaN HEMT by changing the channel carrier concentration and the electric field distribution.(2)The influence of AlN insertion layer on the characteristics of AlGaN/GaN HEMT device is simulated,and the effect of the thickness change on the electrical and subthreshold characteristics of the device is analyzed.After adding AlN insertion layer,the carrier mobility and leakage current of AlGaN/GaN HEMT devices are both improved under the optimal thickness.The average subthreshold slope(SS)is reduced,and it decreases further with the increase of the thickness of AlN insertion layer.That is,the subthreshold characteristics and reliability of devices are optimized.(3)The influence of back barrier structure with different structural parameters on the performance of AlGaN/GaN HEMT devices is simulated,and the reduction of device subthreshold slope is analyzed.After adding different back barrier structures,the subthreshold slope of the device is significantly reduced.After adding the back barrier structure to the AlGaN/AlN/GaN HEMT device,the subthreshold slope of the device is further reduced,that is to say,the switching characteristics of devices in subthreshold region are further optimized.