Fabrication And Electrical Performance Of Junction Device Based On Epitaxial Boron-doped Diamond

Compared with the chemical and solar cells currently used,radiant volt isotope batteries(referred to as radioactive isotope batteries)have the advantages of long service life,high unit energy density,harsh environment resistance,and maintenance-free.It has huge application potential in outer space,polar,deep sea,desert,and other special environments.Compared with other semiconductor materials,diamond has the widest bandgap,high carrier mobility,highest thermal conductivity,good chemical inertness,and excellent radiation resistance,it is the most ideal candidate material for a radioactive isotope battery energy conversion units.However,there are few studies on diamond-based conversion units of radioisotope isotope battery,especially junction devices based on lateral structure Schottky barrier diodes.In this thesis,based on the research of junction devices used in radioactive isotope battery conversion unit,the preparation and characterization of homoepitaxial single-crystal diamond films,and the design and fabrication of lateral structure Schottky barrier diodes are studied in detail,which is expected to improve the potential capabilities of diamond radioisotope batteries via a new route.The specific research content is as follows:(1)To obtain high-quality electronic-grade diamond films with low defect density and roughness,two different geometric sample holder(trapezoidal and flat cylindrical)were designed.The effects of the structure of the sample holder on the growth of homoepitaxial single-crystal diamond films were compared.The results show that under the same growth conditions,the single-crystal diamond film grown on the flat cylindrical sample holder has a smoother surface,low defect density,and high quality,and is more suitable for growing diamond films for device fabrication.(2)Based on the flat cylindrical sample holder structure,using boron as the doping source,the relationship between the crystal quality,doping efficiency and growth temperature of the doped diamond film was studied.The results show that the change in growth temperature will significantly change the surface morphology,crystal quality,and doping efficiency of the doped diamond.Under the condition of using two temperature variables,the surface of the diamond film grown at a higher growth temperature(950°C)results in fewer defects,higher crystal quality,and higher doping efficiency.(3)Based on the flat cylindrical structure sample holder and optimized growth temperature,the effects of different boron doping concentrations on the surface morphology,crystal quality,and semiconductor properties of single-crystal diamond films were studied.The results show that the surface defects of the single-crystal diamond film increase with the increase of boron doping concentration,and the crystal quality decreases.The Hall Effect tests show that the hole concentration increases with the increase of boron doping concentration,but with the carrier migration rate decreases as the carrier concentration increases.(4)Based on optimizing the epitaxial boron-doped diamond growth process and obtaining an epitaxial boron-doped single crystal diamond film with a flat surface and good quality,a detailed and comprehensive exploration of the manufacturing process of lateral diamond Schottky junction devices was made.The influence of mask structure and annealing process on ohmic contact fabrication was investigated by using the metal mask method,vacuum electron beam evaporation,and magnetron sputtering technology.It was implemented on diamond film samples with boron-doped concentrations of 3000 ppm and 6000 ppm.Finally,the development of lateral structure diamond Schottky diodes(Ti/Cu ohmic contact and Cu Schottky contact),further testing of the electrical performance of Schottky barrier diodes show that both samples have obvious rectification performance,and diamond Schottky barrier diode with low boron doping concentration has better diode characteristics,such as a rectification ratio up to 10~5(±4 V).The ideal factor and barrier height are 1.73 and 0.90 eV,respectively.This thesis systematically researches the manufacturing process of lateral structure diamond Schottky diodes,evaluates the basic performance,and ultimately achieves good performance,which will lay a solid theoretical foundation for the application of lateral structure diamond Schottky diodes in radioactive isotope batteries.