| As is known to all,compared with traditional Si materials,the third generation of semiconductor materials GaN has wider band gap width,higher saturation drift speed,thermal conductivity,critical breakdown voltage and other advantages.Therefore,GaN is highly recommended for applications requiring high temperature and high speed and high frequency.Due to the High Electron Mobility Transistor(HEMT)of GaN heterojunction,which is a two-dimensional Electron gas(2DEG)with High conductivity,it can achieve strong current drive capability while maintaining high voltage resistance and low power consumption characteristics.GaN HEMT has become a hot topic in recent years.This paper focuses on the study of the structure of enhanced GaN HEMT devices,aiming at designing an enhanced GaN HEMT device with high breakdown voltage,high threshold voltage,and high saturation drain current.Research and optimization are mainly carried out on the basis of Double Heterojunction Technique,Split-gate Technique and Field Plate Technique.Technology Computer Aided Design(TCAD)simulation tool was used to simulate the internal working process of HEMT,and the working mechanism of HEMT was analyzed and verified.The specific research contents are as follows:(1)The structure and working principle of traditional recessed HEMT are discussed.Compared with the performance of traditional recessed HEMT,double heterojunction HEMT and the improved double heterojunction HEMT,it is found that the improved double heterojunction HEMT can achieve the enhanced function better and achieve stable threshold voltage at the same time among such three device structures.Then,the structure of the improved HEMT was optimized to explore the influence of specific parameters at key levels on the electrical properties of the device,and to reveal the mechanism of the device.The device performance was optimized with prior art,with a threshold voltage of 1.8 V and drain saturation current of 550 m A/mm.(2)In order to further improve the threshold voltage of the device,a split gate structure is proposed based on the improved HEMT.The working principle of the split gate structure is studied and analyzed through the 2D device simulation of Silvaco.Then,the effects of gate length and gate number on device performance are investigated.It is found that if the gate length is set properly,the double-gate structure has better performance than the single-gate and triple-gate structures.The effect of the width and depth of the barrier layer on the threshold voltage of the device is simulated and analyzed.It is found that the threshold voltage will increase gradually with the increase of the width of the barrier layer,but at the cost of drain saturation current loss.Adjusting the depth of the barrier layer has a significant effect on the threshold voltage of the device.The appropriate barrier layer depth not only does not reduce the drain saturation current,but also can obtain a larger threshold voltage.The threshold voltage of the device is increased from 1.8 V to 4.1 V,and the drain saturation current remains at550 m A/mm.Aiming at the voltage resistance of the device,the influence of field plate technology on the device performance was studied,and the voltage resistance of the device was improved to 1200 V by using the double field plate structure combining the gate field plate and source field plate. |
