Research On GaN Quasi-vertical Schottky Diode And Monolithic Integrated Limiter Circuit

With the rapid development of microelectronics technology,the performance of traditional semiconductor devices represented by the first-generation semiconductor silicon and the second-generation semiconductor gallium arsenide has gradually approached the theoretical limits of materials.In the new generation of electronic information systems in the fields of communication radar,energy,and aerospace,there is an urgent need for high-voltage,high-temperature,radiation-resistant,high-frequency,and high-power electronic devices.Therefore,in the past two decades,people have begun to focus on the research of new generation semiconductor materials and devices such as Gallium Nitride（GaN）and Silicon Carbide（Si C）.Among them,GaN electronic devices have significant advantages in the development of power devices and frequency devices such as high breakdown voltage,high frequency,high current,high power density,high temperature,and radiation resistance due to their superior material properties.It has begun to be widely used in 5G communications,radar detection,high-efficiency power supplies and other fields,showing huge development potential and application prospects.However,GaN frequency devices and power devices currently entering the application field are lateral high electron mobility transistors（HEMTs）and Schottky diodes（SBD）,which mainly uses the high-density and high-mobility two-dimensional electron gas of GaN heterostructure as the channel.In contrast,vertical GaN HEMT and SBD devices are more suitable for high-voltage and high-current applications.However,as key scientific and technological issues have not yet been broken through,the development of vertical GaN devices is relatively lagging behind,and research and breakthroughs are urgently needed.At the same time,GaN electronic devices are still mainly discrete devices,and there is an urgent need to carry out research on GaN integrated circuits with more functions,stronger performance,and smaller size.Based on the above research background,this work focuses on the GaN quasi-vertical SBD device structure,key processes and monolithic integrated limiter circuits.The main research results obtained by the paper are as follows:1.Propose and implement a silicon-based GaN quasi-vertical metal-insulator-semiconductor SBD（MIS-SBD）.By inserting an ultra-thin Si N tunneling dielectric layer between the anode metal layer and the GaN epitaxial layer,the hot electron emission current and tunneling current of the device under reverse bias are effectively reduced,and the reverse blocking capability and high temperature characteristics of the device are significantly improved.Compared with the traditional SBD,the reverse leakage of MIS-SBD is reduced by more than two orders of magnitude,the high-temperature leakage is also significantly reduced,and the reverse breakdown voltage is increased from 121 V to 288 V.2.Develop an Al GaN quasi-vertical SBD device with both high forward current density and high reverse voltage.Based on the balanced consideration of the forward and reverse characteristics of the device,an Al_0.3Ga_0.7N material with an Al component of 30%is selected.The fabricated SBD device has a forward turn-on voltage of 1.03 V,an on/off ratio of 10⁹,an ideality factor of 1.22,a forward current of 127 A/cm² at 2 V,and the reverse average breakdown field strength exceeds 2 MV/cm,which is the best result in the world for similar devices.3.Study the performance changes of GaN quasi-vertical SBD under gamma irradiation,explore the influence of the device passivation layer on the irradiation characteristics,and conduct an in-depth analysis of the influence of the passivation layer charge caused by radiation on the device carrier transport mechanism.On this basis,an irradiation model of passivated devices is proposed,which provides theoretical support for the application of GaN quasi-vertical SBD in irradiation environments.4.Design and implement a graded doping quasi-vertical terahertz GaN SBD device.Through the precise design of the epitaxial structure and device structure,and the iterative optimization of the material growth process and device manufacturing process,a novel graded doping terahertz GaN quasi-vertical SBD is realized,which has both high cut-off frequency and high breakdown voltage.The cut-off frequency reaches 710 GHz,the breakdown voltage reaches 28 V,and the Johnson figure of merit f_c·V_br is as high as 20 THz·V,which is the best result in the world for similar devices.5.Develop the world’s first monolithically integrated GaN limiter circuit.Develop a circuit design and manufacturing process platform for monolithic integration of GaN quasi-vertical SBD and passive components,and realize a DC～10 GHz three-level passive limiter circuit based on GaN quasi-vertical SBD.In the DC～4 GHz frequency band,the insertion loss is less than 1 dB.In the 4 GHz-10 GHz frequency band,the insertion loss is basically maintained at around 1 dB,which is relatively low.When the input power is 40 dBm continuous wave,the output power is 26 dBm,which has good limiter characteristics.This quasi-vertical GaN SBD monolithic integrated limiter circuit plays an important role in promoting the development of GaN integration technology.