Design And Key Technology Of Gate-controlled Bipolar Composite-field-effect Transistors

As the core component of electronic power technology,power semiconductor devices have been developed rapidly in recent decades.Various new structures and new technologies have been proposed.With the increasing application requirements,it is necessary to study new power semiconductor devices with higher power,higher BV,higher current and higher integration.Among the existing mainstream power devices,as an unipolar device,power MOSFET has contradictory relationship between BV and R_on,sp,which will limit the application in high voltage range.While the bipolar device power IGBT,which is improved in power MOSFET structure,has become a research hotspot in the field of high power devices due to the characteristics of high BV and high current.Inspired by IGBT structure,in this paper,a novel bipolar field effect composite structure based on the original power MOSFET structure,called GCBT,is proposed and studied.The structure features using the base-gate short connection mode instead of the base-source short connection mode as the traditional VDMOS.In this method,minority carriers can be injected into the active region,and the unipolar device can be changed into bipolar device.Two conductive paths provided by the composite BJT and MOS structure not only improves the integration degree,but also greatly increases the forward on-state current while the breakdown mechanism remains unchanged.The main innovation work and the results obtained in this paper are as follows:(1)Si-based vertical GCBT device is proposed and designed in order to verify the feasibility of the GCBT structure.Its working principle is analyzed and verified by TCAD software,and compared with the traditional VDMOS in dynamic and static characteristics.The simulation results show that the maximum on-state current reaches 7.8×10^-4A/?m,which is more than two orders of magnitude higher than that of VDMOS,and the breakdown voltage remains unchanged while the threshold voltage drops to 1/10 of that of VDMOS.At the same time,VGCBT can work normally as a switch device,and the T_on of VGCBT is about 1/5 of that of VDMOS,and 1/10 of that of VIGBT.But the T_off of VGCBT is 20 times longer than that of VDMOS,which is similar to that of IGBT.(2)SiC-based vertical GCBT device is proposed and designed in this paper to alleviate the existing problems of SiC based devices.It is found that the device does not need p-type substrate,which can significantly improve the high resistance,high diode on-voltage and latch-up effect of SiC IGBT.The comparison simulation results show that SiC VGCBT has excellent static characteristics,including higher breakdown voltage,lower threshold voltage(2.98V)and lower on-state voltage drop.The on-state current is 16.7 times of that of SiC VDMOS with same parameters,28%higher than that of traditional SiIGBT and 71%higher than that of SiC IGBT,and it is almost unaffected by JEFT resistance.In terms of dynamic characteristics,SiC VGCBT has the shortest T_on,and the switching off characteristic of the device are also improved compared with traditional SiC IGBT.(3)SiC-based lateral GCBT devices are proposed and designed to expand the application scenarios of GCBT structure and facilitate integration.The working principle of the device is deeply explored and the performance of the device is comprehensively compared and analyzed.The simulation results show that the maximum forward on-current can reach1.15×10^-3A/?m under the same conditions,which is 15.4 times of that of SiC LDMOS and10 times of that of SiC LIGBT,and can reach a relatively large on-state current when V_G is relatively small.But the dynamic performance is not as good as expected.Although the T_onis short,the T_off time is twice as long as SiC LIGBT,which may limit the application of SiC LGCBT in high frequency.But the device still has good application prospects in high integration,high power and low frequency applications.