GaN HEMT Power Device New Structure Nd Modeling Research

Compared to Silicon (Si) and gallium arsenide (GaAs), Gallium nitride (GaN) havesuperior advantages such as wider band-gap, high thermal conductivity, high criticalelectric field and high electron saturation velocity. High electron mobility transistors(HEMTs) made by GaN, due to its high power density and high speed features,becoming hot topics at home and abroad. This dissertation aims at GaN HEMT physicalmodeling and new structure designing, and the large signal equivalent circuit modeling,the work carried out and innovations are as follows:First of all, In view of the barrier layer doping make device breakdown voltagereduced, proposed novel local doped GaN HEMT structure, the barrier layer of thisstructure only doped under the gate electrode, while the other regions of the barrierlayer are unintentionally doped, widening the depletion layer width between the gateand drain electrodes, enhancing the breakdown voltage of the device. Two dimensionalnumerical analysis results show that, the theoretical maximum output power density ofthe proposed structure is34%larger than that of the entire doped structure. In view ofthe electric field near the drain side gate edge is higher, proposed the recessed gate edgewith source field plate GaN HEMT new structure at the same time, the structure etchedthe barrier layer of drain side gate edge, reduced the electric field strength of the gateedge on the side of drain electrode, increasing the breakdown voltage of HEMT device,so as to enhance the output power density, in addition, the structure decreases the gatedrain capacitance, improving the small signal characteristic. The numerical simulationmethod of unsymmetrical Y shaped gate GaN HEMT device are discussed, and analysedthe influence of different inclination to the device breakdown voltage.Secondly, GaN HEMT devices based on domestic process lines, a large-signal GaNHEMT model including self heating effect is established, which is based on measuredDC I-V curve and S parameters under multi bias condition, and embedded incommercial software ADS by using Symbolic Defined Devices (SDD). The harmonicbalance simulation results show that the model has high precision under the Ku band.Established scaling large signal equivalent circuit model based on Angelov model. Finally, in order to verify the accuracy of the established scalable Angelov model,based on the established1.25mm GaN HEMT large signal model, a S-band poweramplifier modules at class AB is designed. Further proving the accuracy of theestablished nonlinear model in this paper, and the model can be used for practicalapplications. Measured results show that the small signal gain of the power amplifier inthe2.7~3.5GHz is greater than10.5dB, in the frequency range of2.5~3.5GHz, theoutput power greater than34dBm, power added efficiency is greater than41.5%.