Research On Power Loss And Integrated ESD Protection Of Power P-Type Gate GaN HEMT

At present,enhancement-mode p-Ga N HEMTs are promising candidates to achieve high-efficiency,high-frequency,high-temperature power conversion and have been used in commercial application.However,in the application,there are some problems,such as low power-loss model accuracy and electro static discharge(ESD)reliability.Aiming at the problems encountered in the application-oriented process of p-type gate Ga N HEMT power devices,this dissertation studies the power loss model,high-temperature power loss and new structure integrated with ESD protection for p-type gate Ga N HEMT power devices.The main innovations are as follows:(1)An analytical switching loss model for low-voltage buck converters based on ptype gate Ga N HEMT power devices is established.Aiming at the problem that the power loss model evaluation accuracy and speed of p-type gate Ga N HEMT power devices need to be further improved,by analyzing the switching characteristics of p-type gate Ga N HEMT power devices in buck converters,a piecewise linear approximation method is used to establish a model suitable for low-voltage Ga N-based buck converters.This model not only includes the control switch’s switching loss,but also the synchronous rectifier’s switching loss.Based on this model,the power loss and efficiency of the buck converter can be evaluated.The results show that the analytical model is in good agree with simulation and experimental measurement.Experimental results show that the evaluation accuracy of efficiency and power loss are improved by 52.3% and 66.1%,respectively,using the proposed switching loss model for the 12 V～1.2 V buck converter when the operating frequency is from 400 k Hz to 1 MHz and the output current is from 5A to 15 A.The power loss model provides a fast and accurate evaluation scheme for the power loss calculation of buck converters based on p-type gate Ga N HEMT power devices,and provides research guidance for the follow-up work of this dissertation.(2)The physical mechanism of the increase in capacitance of p-type gate Ga N HEMT power devices caused by the decrease of barrier height at high temperature is revealed.Aiming at the problem of insufficient research on the high temperature characteristics of converters based on p-type gate Ga N HEMT power devices,by testing the power loss of buck converters based on p-type gate Ga N HEMT power devices at different operating temperatures,and in guidance of the proposed power loss model,the changes of switching loss and conduction power loss of p-type gate Ga N HEMT power device under different temperature conditions are analyzed.It focuses on the change of parasitic capacitance that causes the switching power loss of p-type gate Ga N HEMT power device,and reveals the physical mechanism of the increase in capacitance at high temperature.The physical mechanism can be explained by the high temperature-induced barrier lowering effect under the gate.Under the high drain voltage,the lowering of the potential barrier increases the intrinsic charge,which eventually leads to the increase in the input,output and transfer capacitances.Based on the analysis of the high-temperature characteristics of the p-type gate Ga N HEMT power device,it is found that the power loss of the control switch and the synchronous rectifier increases significantly with the increase of temperature,which is the main source of power loss when the converter operates at high temperature.(3)A novel p-type gate Ga N HEMT power devices with self-triggered discharging channel is proposed.By TLP testing,the ESD reliability of p-type gate Ga N HEMT power device is investigated,and it is found that the ESD reliability between the gate and source could not meet the industrial standard.The failure mechanism between the gate and source for p-type gate Ga N HEMT power device is analyzed,and it is found that the failure results from the special Metal/p-Ga N/Al Ga N gate structure of the devices.Based on the problem that p-type gate Ga N HEMT power device is prone to failure under ESD conditions,a novel p-type gate Ga N HEMT power device with high gate-source ESD robustness is proposed.The new power device has a self-triggering discharging channel,which is composed of a small-sized p-type gate Ga N HEMT and two 2DEG channel resistors.The simulation results show that the ESD failure voltage between the gate and source of the novel Ga N HEMT with self-triggered discharging channel can be increased by 1900% compared to the conventional p-type gate Ga N HEMTs.Finally,based on the domestic Ga N process platform,we fabricated the novel Ga N HEMT.The experimental results show that the gate-to-source human-body model passing voltage of the novel Ga N HEMT is 2.04 k V,which can meet the industry standard.