Optimization Design Of Gate Structure Of β-Ga₂O₃ Field Effect Transistor（FET） For Self-heating Effect And Threshold Voltage Regulation

In recent years,high efficiency and energy saving have become the main goals of the development of power electronic technology.For this reason,researchers are committed to developing power electronic devices with better performance.Due to its good transport properties and large BFOM,β-Ga₂O₃ materials and their power devices have been widely concerned,and have gradually become a research hotspot.Aiming at the problems of poor thermal conductivity ofβ-Ga₂O₃ and the difficulty of achieving high-efficiency p-type doping,this paper uses the Silvaco TCAD to construct a newβ-Ga₂O₃ back-gate field effect transistor（FET）and research the self-heating effect mechanism.At the same time,Al N/β-Ga₂O₃ enhanced HEMT were designed by constructing various gate structures,and the device performance was systematically studied.The main conclusions reached are as follows:Forβ-Ga₂O₃ MOSFET,the back-gate FET device is designed and its self-heating effect is studied in detail.Hf O₂,Al₂O₃ and Si O₂ were selected as the dielectric layers of the back-gate respectively.The research results of the electrical properties of the device showed that the higher the dielectric constant of the back gate dielectric layer material,the higher the output characteristics of the device.In order to reduce the influence of self-heating effect on the device,diamond and h-BN with better thermal conductivity are selected as the dielectric layer of the back-gate.The results show that simply replacing the material with better thermal conductivity as the dielectric layer of the device cannot effectively suppress the influence of the self-heating effect.The current decay caused by the self-heating effect is closely related to the drain current density controlled by the longitudinal electric field of the device.Therefore,two kinds of composite Al₂O₃/h-BN back-gate dielectric layers,vertical and horizontal,are designed in this paper,and the influence of self-heating effect on the device can be effectively reduced by adjusting the vertical electric field distribution.The two structures reduce the current decay rate caused by the self-heating effect from80.15%to 68.10%and 69.63%,respectively,enabling the device to obtain better performance in a high-voltage environment.Further studies have shown that horizontal composite structures have better results than vertical composite structures.For the Al N/β-Ga₂O₃ HEMT,a high-performance Al N/β-Ga₂O₃ depletion-mode HEMT device is designed and simulated in this paper.The interface charge density at the Al N/β-Ga₂O₃heterojunction interface reaches 1.537×10¹³ cm^-2.In this structure,as the thickness of the Al N barrier layer increases,the threshold voltage drifts negatively,the transconductance decreases,and the drain saturation current decreases.At the same time,an enhancement-mode Al N/β-Ga₂O₃HEMT is realized through the structure of groove gate,p-Ga N and polarization neutralization layer.Among them,the polarization neutralization layer utilizes the polarization of In-containing ternary alloys（In Ga N and In Al N）and Al N to generate negative polarization charges at the interface between the polarization neutralization layer and the Al N layer.The floating gate formed by the negatively polarized charge depletes the 2DEG channel and realizes enhancement-mode device.In addition,the double gate structure is introduced into the groove gate structure in this paper,which effectively improves the output characteristics of the device,and realizes the dynamic regulation function between the depletion-mode and the enhancement-mode through the back-gate voltage.Finally,the design idea of introducing a gate dielectric layer into the p-Ga N structure is proposed,which effectively improves the threshold voltage of the device,and realizes the regulation of the device performance by changing the material and thickness of the gate dielectric layer.In this paper,two main problems ofβ-Ga₂O₃ are studied through modeling and simulation of semiconductor devices.Firstly,a method to improve the poor resistance to self-heating effect ofβ-Ga₂O₃ devices is proposed,which provides a new idea for further improving the performance ofβ-Ga₂O₃ MOSFET.The research on the structure design and performance of Al N/β-Ga₂O₃ HEMT will lay a theoretical foundation for the realization of high-performance enhancement-modeβ-Ga₂O₃ based HEMT in the future.