Design Of Device Structure Of GaN-based Enhancement-mode P-channel HFET

GaN HEMTs have the advantages of small parasitic capacitance,high 2DEG mobility,and high breakdown voltage,making them suitable for the application of high frequency and high voltage.However,due to the large parasitic inductance caused by the peripheral circuit of the GaN HEMTs power device,the actual operating frequency of HEMTs is much lower than its theoretical value.The All-GaN monolithic integration technology integrating logic signal generation,drive control,power conversion,monitoring and protection modules into a single chip can minimize the parasitic effect caused by chip interconnection and give full play to the high-frequency and high-efficiency core performance of GaN HEMTs.Due to the lack of mature GaN P-channel transistors(P-HFETs),the All-GaN IC can only rely on N-channel transistors(N-HEMTs),resulting in complex circuit design,high static power consumption,and imperfect functions,which severely limits the development and application of GaN ICs.P-HFETs with good performance can not only simplify GaN IC design,but also improve GaN IC performance.In view of the above problems,this thesis focuses on the research of the recessed gate enhancement mode GaN P-HFETs with high current capability.The main research contents are as follows:1.Achievement of high current density enhancement-mode(E-mode)GaN P-HFETs on the P-GaN/AlGaN heterojunctions.(1)Based on TCAD Sentaurus simulation,the thickness and Alcomposition of AlGaN barrier layer of GaN P-HFETs were optimized,and 2DHG density is 5.8e10¹² cm^-2.In addition,recessed gate structure is used to realize the enhancement mode GaN P-HFETs,and the threshold voltage and current capability of the device are enhanced by optimizing the thickness of the recessed gate and the gate dielectric layer.When the AlGaN layer thickness and Alcomposition are 18 nm and 0.25,the thickness of the recessed gate is 10nm,and the thickness of the gate dielectric layer is20 nm,the threshold voltage and on-current of the device are-0.78 V and 4.44 m A/mm,respectively.(2)A recessed-gate E-mode GaN P-HFETs treated with fluorine is proposed to improve the current capability of the device.Using fluorine to treat the top GaN layer and AlGaN barrier layers of GaN P-HFETs,due to the strong electronegativity of fluorine ions,the energy band structure of the GaN layer and the P-GaN/AlGaN interface can be adjusted.Thereby,it can increase the holes concentration and the on-current of the device.When the fluoride ion concentration in GaN and AlGaN is 2.6e18 cm^-3 and 2e18 cm^-3,respectively,the on-current of the device is 11.48 m A/mm and 7.2 m A/mm,and the threshold voltage is-1 V and-0.52 V,respectively.(3)A recessed-gate E-mode GaN P-HFETs based on a graded Alcomposition AlGaN barrier layer is proposed.The 2DHG concentration and the current density of the device can be improved by optimizing the Alcomposition in graded Alcomposition AlGaN layer.When the Alcompositions x₂,x₁and x of the AlGaN layer are 0.15,0.20 and 0.25,respectively,the on-current of the device is6.46 m A/mm and the threshold voltage is-0.56 V.2.The design of GaN CMOS based on the P-HFETs with F treatment or graded Alcomposition AlGaN barrier layer.The designed recessed-gate E-mode GaN P-HFET with F treatment or graded Alcomposition AlGaN barrier layer and P-GaN gate E-mode N-HEMT are integrated into CMOS.The performance of CMOS is be optimized by optimized the device width of the GaN P-HFETs(Wp).When the width of GaN P-HFET device is 10 times wider than the N-HEMT,the switching threshold of CMOS is about2.5 V,and the output signal of the CMOS can swing from the rail of V_DD to the rail of GND.