Research Of Novel Structures For Power Devices And For Single Event Burnout Hardening Based On Enhancement-mode GaN MISFET

With the gradual development of science and technology,the traditional first-generation semiconductor silicon(Si)-based semiconductor devices have gradually been unable to meet the increasing demand for high-power and high-frequency devices,while the limitations of the second-generation semiconductors gallium arsenide(GaAs)and indium antimonide(InSb)have become increasingly prominent.In order to solve these problems,it is particularly important to carry out the research on third-generation semiconductor devices.The third-generation semiconductors mainly include gallium nitride(GaN)and silicon carbide(SiC),which have inherent advantages over traditional first and second generation semiconductor devices.As a wide-bandgap semiconductor,GaN has high critical breakdown electric field and it has a wide range of application prospects in the application of power devices.At the same time,GaN and AlGaN can form a high concentration of two-dimensional electron gas at the interface which make the device has low resistance.GaN devices have very low energy consumption during application and high energy transmission efficiency becaues of low resistance characteristics.GaN devices play an important role in high-voltage,high-frequency and high-temperature applications.In addition,GaN material has high radiation tolerance,which has great advantages in application of radiation environment.Although GaN devices have attracted the attention of the researchers in recent years,the theoretical research is still very lacking.To make full use of high frequency and high radiation resistance,it is necessary to study GaN materials deeply for now.This article selects the field plate conventional AlGaN/GaN Metal Insulator Semiconductor Field Effect Transistor(FPC-MISFET)as the basic device to analyze the leakage current path and peak electric field of the GaN MISFET device in simulaton/.Developing the breakdown mechanism research of GaN MISFET devices,and propose new structures with improved breakdown voltage.The new structures increase the breakdown voltage of the device while maintaining the low on-resistance of the device,thereby improving the power quality factor VBK2/RON(Baliga’s Figure of Merit,BFOM)of the device.In addition,the thesis will also study the single-event burnout effect of the conventional structure and the hardened structure.The main innovations of the thesis mainly include:(1)Design a GaN MISFET device with a partial AlN buried layer structure(AB-MISFET).The AB-MISFET device has an epitaxial part on the basis of a complete nucleation layer.The AlN buried layer can not only ensure the flatness of the internal layers of the device,but also form an AlN/GaN heterojunction in the buffer layer.This heterojunction can change the current path inside the device and has a drain bias voltage,Under this conditions,part of the electric potential will form a very high voltage drop at this heterojunction.With forming a higher peak electric field in the buffer layer,the average electric field of device increases,and the breakdown voltage of the device is relatively high.In addition,the AlN buried layer is far from the channel layer,which has almost no effect on the two-dimensional electron gas and gate charge on the surface.At last,the on-resistance and the threshold voltage of the AB-MISFET device keep almost same.(2)Design a GaN MISFET with embedded PN junction structure(EJ-MISFET).The EJ-MISFET introduces an embedded PN junction between the gate and the drain.A new peak electric field can be introduced between the gate and the drain under a high drain bias voltage because of the PN junction.This peak electric field can increase the average electric field strength between the gate and the drain,thereby improving the breakdown voltage of the device.(3)Design a double channel GaN MISFET with P-buried layer(DCP-MISFET).In the DCP-MISFET,the second barrier layer and the second channel layer can form a new two-dimensional electron gas in the buffer layer.It is connected to the drain and the buffer layer.Due to the low resistance of the two-dimensional electron gas,part of the potential of the drain voltage will be distributed in the place where the two-dimensional electron gas contacts with the buffer layer.A large voltage drop will form a peak electric field here.This peak electric field helps to balance the distribution of electric field betweem gate and drain.At the same time,the DCP-MISFET device will introduce a P-type GaN buried layer under the gate field plate.The P-type GaN buried layer greatly reduces the peak electric field at the right edge of the gate field plate.Because the P-type GaN buried layer,the second barrier layer and the second channel layer are all located in the buffer layer,the electric field inside the device has also been significantly improved,thereby increasing the breakdown voltage of the DCP-MISFET device.(4)Study the mechanism of single event burnout effect of GaN MISFET devices.The incident of heavy ions into the GaN MISFET is simulated.According to the triggering process of the single event burnout(SEB)of the device,the mechanism for the single event burnout of the device is analyzed.According to the triggering process of the single event burnout of the device,it is analyzed that the mechanism of the single event burnout of the device is due to the avalanche breakdown of the device.Because of the high concentration of electrons,holes and the high peak electric field around the drain in the later stage after heavy ion incidence,the device is burned out.According to the conclusion,the single-event burnout performance of AB-MISFET devices,EJ-MISFET devices and DCP-MISFET devices was verified.EJ-MISFET devices and DCP-MSIFET devices improve the device’s ability to resist single event burnout by reducing the electric field near the drain after heavy ion incidence.