Preparation And Characterization Of P-CuAlO₂ Films By Sol-gel Method On Sic Substrates

In order to solve the problem of low injection efficiency of p+n emitter junction caused by incomplete ionization of P-type SiC in bipolar SiC power devices,our research group proposed to use the heterojunction formed by wide bandgap P-type CuAlO₂ and N-type SiC as the emitter junction.In order to improve the injection efficiency of the junction.In this paper,based on the Sol-gel method(Sol-gel),the preparation process of CuAlO₂ film on 4H-SiC substrate was studied.For the first time,CuAlO₂ film and CuAlO₂/SiC heterojunction were prepared on SiC substrate,and their characteristics were studied..The main research work and results are as follows:1.The influence of the preparation process on the structure and properties of CuAlO₂ films was studied.The structural properties of the films prepared at four different concentrations of 0.1mol/L?0.3mol/L?0.5mol/L and 0.7mol/L are tested.The results show that as the sol concentration increases,the diffraction peak intensity of the film increases,The crystallinity is improved.When the sol concentration is 0.7mol/L,the film prepared has the largest grain size,with a particle size of about 35nm;for the four different pretreatment temperatures of 150??200??250? and 300?,The test results of the structure and properties of the film show that a higher pretreatment temperature is helpful for the crystallization of the film.When the pretreatment temperature is 300?,the film prepared has the best crystallization quality;annealing under air,oxygen and nitrogen shows that the result shows that nitrogen The atmosphere is more conducive to the crystallization of the film;high temperature annealing at 800??900??1000??1100?,the results show that as the annealing temperature increases,the crystal quality of the film increases and then decreases.When the annealing temperature is 1000?,the crystallinity of the film is higher.2.The influence of the preparation process on the optical and electrical properties of CuAlO₂ thin films was studied.Through optical testing of films prepared at different concentrations,different pretreatment temperatures and different annealing temperatures,the results show that the light transmittance of the film decreases with the increase of sol concentration and pretreatment temperature,and with the increase of annealing temperature Higher and higher,the average transmittance in the visible light range is greater than 70%,and the optical band gap is 3.85 eV;through the PL test,it can be seen that near ?=359nm,?=380nm,?=410nm,?=470nm.The four emission peaks correspond to the ultraviolet near-band edge emission peak of CuAlO₂,the band edge emission peak of SiC,and the two copper vacancy defect peaks.The conductivity type of CuAlO₂ films after annealing at 800??900??1000??and 1100? are all P-type.The conductivity,carrier concentration and mobility of the film increase and then decrease with the increase of annealing temperature.The film with the best electrical properties can be obtained by high temperature annealing at 1000?.Its mobility,carrier concentration and conductivity are 16.13cm2/V·s,3.92×1017cm3 and 1.01S·cm-1,respectively.3.The electrical characteristics of the p-CuAlO₂/n-SiC heterojunction are studied.The results show that the p-CuAlO₂/n-SiC heterojunction has good rectification characteristics,and the turn-on voltage is about 1.6V.when the applied voltage is 13 V,The rectification ratio of the heterojunction is 1.26×103,and the hole/electron injection ratio is 7.15×109 calculated by theoretically analyzing the energy band structure of the heterojunction.The above preliminary research results indicate the feasibility of p-CuAlO₂/n-4H-SiC heterojunction in bipolar SiC devices.