Simulation Investigation Of Downscaled Wide Bandgap Semiconductor Field Effect Transistor

Wide-gap semiconductor materials represented by gallium nitride,silicon carbide,diamond,etc.,have the advantages of large bandgap width,high carrier mobility,and strong breakdown field,which are very suitable for applications in high-frequency and high-power electronic devices.Therefore,with the development of the semiconductor industry,wide bandgap semiconductor material devices are gradually replacing the application of some silicon-based semiconductor devices,especially in terms of high frequency,high power,and high voltage.In general,in order to obtain better frequency characteristics and power characteristics,the scale of semiconductor devices is continuously reduced,and the gate length is reduced from micrometers to nanometers.The proportional reduction of the size of semiconductor devices can improve the basic performance of the device.However,as the gate length of the device is reduced to a certain length,the device will inevitably appear short channel effects and other non-ideal characteristics,making the device Can not achieve the desired result we expected.This thesis aims at the representative GaN heterojunction high electron mobility transistors in wide bandgap semiconductors and hydrogen-terminated diamond field effect transistors in p-type devices,using Silvaco TCAD software to scale down the devices of the two devices.The characteristics are systematically studied,and the non-ideal characteristics of the device appearing in the process of proportional reduction are in-depth researched to provide a theoretical basis for the experimental research of the device.The specific work content and conclusions are as follows:1.Summarize the device structure of gallium nitride devices when scaled down from the reported papers,and formulate the reduction law of HEMT devices in this article.Analyze the DC characteristics and frequency characteristics of GaN devices when the gate length is reduced from 600 nm to 50 nm,so as to provide certain experience for the proportional reduction of hydrogen-terminated diamond MOSFETs.In the process of scaling GaN HEMT devices,the threshold voltage,transconductance,and saturation drain voltage of the device decrease approximately linearly with the decrease of the thickness of the top barrier layer.The transconductance was increased from 244 m S/mm to 982 m S/mm,and the cutoff frequency was increased from 28 GHz to 236 GHz.Although a certain short channel effect still appears when the gate length is less than 150 nm,under this proportional reduction rule,the device still maintains DC and AC characteristics as the gate length decreases,compared to the following The short channel effect of diamond is reduced in the article.2.In this paper,the direct current performance and cut-off frequency(f _T)of H-diamond FETs with the gate length(L_G)downscaling from 2?m to 50 nm are investigated by two-dimensional device simulation.For our central-gated device with a 10-nm-thick Al₂O₃gate dielectric,the transition point of L_Gfrom the long-channel behavior to the short-channel one is found to be 150 nm.Though notable short-channel effects appear for L_G?150 nm such as the negative shift of the threshold voltage and the increase of the DIBL,the knee voltage at a given gate voltage stays almost a constant for all the considered gate length range,which is unfavorable for small-size device with lower operation voltage.From f _T^-1versus L_Grelation for L_G?150 nm it is found the effective velocity in the channel of H-diamond FETs at the drain voltage not more than 9 V is less than a half of the saturation velocity.In summary,this paper uses two-dimensional simulation software Silvaco to establish simulation models of Ga-face GaN HEMT devices and hydrogen-terminated diamond MOSFET devices.The device structure is scaled down in different ways,and the basic performance of the device changes with the channel length,and the impact of the short channel effect on the device.The side analyzes the difference between the two devices when scaling down.It provides a foundation for the application of GaN and hydrogen-terminated diamond small-size devices.Provide help for the application of GaN and hydrogen-terminated diamond small-size devices and the use of gallium nitride and diamond to make complementary devices.