Research On New Gallium Oxide Power Device

Gallium oxide（Ga₂O₃）materials have the advantages of ultra-wide bandgap and high critical electric field.Compared to silicon and the third generation of semiconductor devices,Ga₂O₃-based devices perform very well in terms of breakdown voltage（BV）and on-state loss.But Ga₂O₃ material is currently difficult to achieve controlled high-quality P-type doping and epitaxy,so Ga₂O₃-based MOSFETs are limited in variety;Meanwhile,the development of superjunction structures,which are widely used in silicon-based applications,has been bottlenecked by the difficulty of implementing P-type Ga₂O₃.In this thesis,a new depletion mode Ga₂O₃ LDMOS device with superjunction is designed by introducing a P-type doping material to improve the problem of difficult to achieve controllable high-quality P-type doping and epitaxy in Ga₂O₃.And the concept of Ga₂O₃IGBT was also proposed.Moreover,based on the existing research progress,the P-type region in Ga₂O₃ by diffusion is introduced to design enhancement mode Ga₂O₃VDMOSFET device.And then the electrical and thermal characteristics of these devices were analyzed,and the specific work is organized as follows:1)A lateral superjunction Ga₂O₃ LDMOS structure using P-type diamond is proposed.To address the problem that it is difficult to achieve P-type doping in Ga₂O₃,P-type diamond and N-type Ga₂O₃ are introduced to form a lateral superjunction,and the heat dissipation efficiency of the device is greatly improved.The device achieves a larger BV and a smaller specific on-resistance(R_on,sp)while maintaining a higher drift region doping,improving the performance of the device.Numerical simulation results show that the BV of the proposed device is 7000 V and the R_on,sp is only 23.22 mΩ·cm²,which improves the breakdown voltage by 133%and reduces the R_on,sp by 82.3%compared with the conventional Ga₂O₃ LDMOS with field plate.The turn-on time of the proposed device is reduced to 3.6 ns,the turn-off time is reduced to 26.15 ns,and the junction temperature variation of the proposed device is reduced by up to 92.2%.2)A normally off enhancement mode Ga₂O₃ VDMOS structure using P-type nickel oxide（Ni O）is proposed.The proposed device uses heavily doped P⁺Ni O instead of the metal gate in the conventional structure,which increases the channel width of the proposed device.And the introduced P-type Ga₂O₃ region below the gate trench shields the high gate electric field of the gate oxide.Numerical simulation results indicate that the BV of the proposed device is 7500 V and the R_on,sp is only 6.71 mΩ·cm²,which increases the BV by 25%and reduces the R_on,sp by 36.3%compared with the conventional Ga₂O₃ VDMOS.The turn-on and turn-off time of the proposed device are reduced to 40.5ns and 45 ns,respectively.3)A trench gate Ga₂O₃ IGBT structure using P-type Ni O is proposed.By introducing the P⁺type region in the IGBT structure with a heavily doped P⁺type Ni O,the basic Ga₂O₃IGBT performance is successfully achieved and the feasibility of the Ga₂O₃ IGBT is verified.Numerical simulation results display that the BV of the proposed device is as high as 9550 V and the R_on,sp is as low as 1.25 mΩ·cm².According to the results of this thesis,it can be seen that Ga₂O₃-based power devices have a very good compromise between BV and the R_on,sp,and will be a priority direction for the development of future power semiconductor devices.