Deep-Level Characteristics Of Bulk Diamond And Its Effect On Optical Properties

The unique electrical,optical,mechanical properties of diamond make it an ideal material for optoelectronic devices at present especially in strict enviroments such as high temperature,high radiation and corrosion environments.However,the growing diamond material inevitably introduces impurities and defects.If harmful impurities or defects form deep levels in the forbidden band of the diamond material,these deep levels can capture electrons or holes,thereby promoting carrier recombination,which would results in shorting the lifetime of minority carriers,reducing the mobility of majority carriers and ultimately affecting the performance of optoelectronic devices such as diamond ultraviolet detectors.In order to quantitatively analyze the trap level in diamond,a high-performance diamond device is fabricated.In this paper,diamond crystal is used as the research object.Firstly,the electrode contact of diamond is prepared and the influence of different electrode spacing on the diamond light response is tested.The deep level transient spectrum test tests and characterizes the deep level traps in the material.Finally,the simulation calculates the influence of the deep level on the optical properties of the diamond material.On this basis,there is a goal to achieve effective control of the deep energy level in the diamond growth process and subsequent processing processes to obtain high-quality diamond materials,laying the foundation for the wide application of high-performance photovoltaic devices such as diamond ultraviolet detectors.The main contents of this paper are as follows:(1)The contact preparation of the diamond material is carried out,and the contact of the diamond material is basically tested by the semiconductor device tester,and the influence of different electrode spacing on the diamond light response is tested and analyzed.(2)Deep level traps in diamond materials are studied using deep level transient spectroscopy(DLTS)techniques.First,considering that the test parameters of deep level transient spectrum(DLTS)have a great influence on the test results,this study improves and optimizes the parameters during the test,and designes the test flow according to the improved parameters;Transient,Isothermal transient spectrum(ITS),and temperature scanning(Tempscan)techniques are used to test the deep level defects of diamond materials.Fourier transform is used to analyze the results.Three trap levels were obtained at 200 K,540 K,and 726 K,and the three trap level activation energies,capture cross sections,and carrier concentration are obtained by Arrhenius curve fitting.Finally,the high-energy resolution analysis(HERA)is used to separate and analyze the deep-level overlapping emission process of diamond.The results show that the trap energy levels of two activation energies are separated in the trap energy level of 540 K,which cannot be achieved by the traditional maximum value analysis,thus achieving systematic characterization and quantitative description of deep levels in diamond materials.(3)Using the first principle of density functional theory,the optical properties of deep-level diamond and eigenstate diamond are simulated and analyzed.The results show that the trap level can cause the light absorption coefficient of diamond material to decrease and a significant phenomenon are presented in the high energy region greater than 11.4 e V which called”red shift”,the dielectric function in the low-energy region of less than 5 e V can reach 3.8times the maximum peak of the eigenstate,which also leads to a decrease in conductivity and an increase in the loss function.These phenomena all indicate that the trap level damages the optical properties of diamond,so it is possible to improve the performance of photovoltaic devices such as diamond ultraviolet light by controlling the generation of trap levels in diamond materials.