Terahertz Frequency Multiplier Characteristics And Applications Of Schottky Barrier Diode With Metal-Brim Structure

Stable and reliable terahertz source is the basic condition for the wide applications of terahertz technology.Frequency multiplier based on Schottky barrier diode?SBD?is an important part of terahertz solid-state source.Due to the lower reverse breakdown voltage and larger leakage current of Schottky barrier diode and the limitation of the fabrication technology of terahertz monolithic integrated frequency multipliers,the operating frequency and output power of the terahertz monolithic integrated frequency multipliers independently developed in China are not high at present.At the same time,power leakage which is caused by tunneling effect and interface defect charge of the SBD becomes more obvious with the increase of input power and operating frequency.Therefore,the domestic research on THz frequency multiplier monolithic microwave integrated circuit?MMIC?is still in the lower frequency band.The main contents of this paper are as follows:In view of the problems above,this paper mainly focuses on the key technologies involved in the realization of multiplier MMIC,including the study on the terminal structure of THz SBD,the realization and optimization of multiplier MMIC,the physical model of Schottky barrier varactor?SBV?,and the research on Ga N-based THz SBV.?1?Study on the terminal structure of THz SBD.Aiming at the problems of the lower breakdown voltage and larger leakage current of SBD,the SBD with a novel terminal structure named metal–brim is proposed.Metal-brim structure has simple manufacturing process,lower cost,and could be well integrated in the terahertz monolithic circuit fabrication process.Metal-brim structure improves the reverse characteristics by eliminating the accumulation effect at the edge of electric field and reducing the leakage current caused by the reduction of fringing barrier,which is manifested by the increase of breakdown voltage and the decrease of leakage current.When metal-brim structure is applied to SBD with Schottky diameter of 3?m,the breakdown voltage is increased by 19.6%compared with the conventional structure.?2?Realization and optimization of multiplier MMIC.The fabrication technology of metal-brim terminal structure based on dry etching and wet etching was developed,and the multiplier MMICs based on SBD with metal-brim terminal structure were completed.Compared with conventional structure,the metal-brim structure can improve the performance of the multiplier MMIC,and the mechanism of metal-brim terminal structure to improve the performance of the multiplier is analyzed.The metal-brim structure can reduce the leakage current of SBD and improve the nonlinear I-V characteristics,which provides a feasible scheme for the design of frequency multiplier.?3?Research on the physical-based model of SBV with metal-brim structure based on tunneling effect.To solve the problem that the traditional model can not accurately describe the power leakage caused by interface defects and tunneling effect,the physical model based on tunneling effect is proposed which could also be used to harmonic balance simulation.The interface defects caused by metal induced gap state?MIGS?and dangling bonds on the semiconductor surface can cause thermionic emission current damping and extra tunneling effect,thus resulting in the decrease of capacitance modulation ration.The interface defect is equivalent to an ultra-thin dielectric layer between Schottky metal and semiconductor,and the thickness of the dielectric layer is calculated by using Metal-Insulator-Semiconductor?MIS?energy band structure.Finally,the physical basis model is established and the equation which can satisfy harmonic balance simulation is proposed.The validity of the model is verified by the simulation of 215GHz frequency tripler.?4?Preliminary study on Ga N-based terahertz SBV with metal-brim structure.Compared with Gallium Arsenide?Ga As?,the thermal conductivity and breakdown field strength of the third-generation semiconductor material Ga N have been greatly improved,which meets the design requirements that frequency multiplier can withstand high input power.Our research focuses on solving the problems of poorer breakdown characteristics and higher ideality factor of Ga N-based SBV.Ga N-based SBV based on metal-brim terminal structure is designed,and the simulation results show that the breakdown voltage could reach-36.1V when the thickness and doping concentration of epilayer are 300 nm and 2×10¹⁷/cm³.