Field Distribution Model Of The New AlGaN/GaN HEMT With Electric Field Modulation Effect

AlGaN/GaN high electron mobility transistor(HEMT)devices have great application potential in power processing,high temperature environment,large frequency and so on,they have been paid much attention by researchers because of their excellent characteristics.When the device works under the condition of high power for a long time,the junction temperature in the device will rise and produce the self-heating effect,an appropriate device models can provide theoretical guidance for people to design and optimize devices,thus shortening the research and development cycle and production cost of HEMT devices.But at present,researchers mainly focus on the large signal applications of HEMT devices modeling,the modeling and analysis of the channel potential and electric field distribution in the state of the HEMT device is less.The existing models are mainly suitable for the cases where the drain voltage of the device is small.The modeling of the device under the condition of high drain voltage is worthy of further study.In addition,in order to explore the effect of reduced surface field(RESURF)technology on the temperature field distribution of the device,we observed the temperature-varying electrical characteristics and channel junction temperature distribution of the device by means of software simulation and experimental measurement analysis.First of all,a two-dimensional analytical model for channel potential and electric field distribution of RESURF AlGaN/GaN HEMT HEMT devices is proposed in this paper.The model takes into account the difference of the surface density and length of the doped negative charge,thickness and Al component of AlGaN and the gate length.There is a good agreement between the analytical model and the simulation results of TCAD software,and the model can reflect the specific effect of device parameters on the electric field distribution.It is also applicable in the case of large drain voltage,which has certain theoretical guiding value for the design of high voltage HEMT devices.In the two dimensional(2D)simulation of the channel temperature field distribution of the device,we found that the junction temperature of the AlGaN/GaN HEMT device with a stepped AlGaN barrier layer is lower under the same working conditions,and the junction temperature is decreased with the increase of the etch depth of the barrier.When the fixed length of the etch is 4 ?m and the etch thickness is 15 ?m,the average junction temperature of the device is reduced by 35.3% and 18.2%,respectively,compared with the conventional device and the device having a step thickness of 5 ?m.Then,the electrical characteristics of AlGaN/GaN HEMT devices at room temperature to 200? have been measured,and the characteristics of two dimensional electron gas(2DEG)have been studied.The degradation of electrical characteristics of the devices at high temperature has been observed.The saturation leakage current and transconductance decrease,threshold voltage drift.It is found that compared with the conventional AlGaN/GaN HEMT,etching on the AlGaN barrier layer can alleviate the degradation of the DC characteristics of the device with the increase of temperature.When the temperature is 90?,200?,the maximum output current of the conventional device and the device etched with the AlGaN barrier layer is reduced by 28% and 45%,18% and 32%,respectively.The limitation of 2DEG becomes worse,and the mobility of carriers becomes smaller,which can explain the degradation of the electrical characteristics of the device to some extent.Finally,compare the different junction temperature measurement methods of the device,combined with the actual situation of the device,we measured the junction temperature of the device by Raman spectroscopy.The results show that the junction temperature distribution of AlGaN/GaN HEMT device with etched AlGaN barrier layer is lower under the same dissipative power,when the power dissipation is 0.2 W and 0.3 W,the average junction temperature of the device with a groove depth of 15 ?m is 33.8% and 28.4% lower than that of the conventional device,which is of great significance for improving the hightemperature reliability of the device.By numerically modeling the device's channel electric field and simulating and measuring the temperature field distribution of the device,we can see that RESURF technology reduces the channel junction temperature of the device while modulating the surface electric field distribution of the device and stabilizes the high temperature characteristics.The power characteristics and high temperature reliability of AlGaN/GaN HEMT devices are linked.