N-BN Band Gap Engineering Based On N Vacancy Defect

Hexagonal boron nitride?h-BN?is a wide bandgap semiconductor with extraordinary properties,including high temperature stability,good chemical resistance,high breakdown field strength and large thermal conductivity.The h-BN based UV detectors have the advantages of small size,low dark current,high radiation resistance,etc.But,the bandgap of h-BN is wider than 5.7 eV,which makes the absorption band edge out of the solar-blind UV?220-280 nm?range.This will limit the usage of h-BN based UV detectors.Therefore,the modulation of h-BN bandgap is needed to make the absorption band edge into the solar-blind UV range.This paper focuses on analyzing how N-vacancy affects the bandgap of h-BN by first-principle calculation and implementing the modulation of bandgap of high-quality h-BN membrane.The contents and results of this paper are as follows:?1?First-principle calculation of h-BN band.The result indicates that N-vacancy will introduce the donor level.And with N-vacancy density increasing from 0.31%to18.75%,the bandgap of h-BN will decrease in 2.40 eV.Besides,the calculation indicates that B-vacancy will introduce the acceptor level and make the bandgap of h-BN 2.08 eV narrower,with B-vacancy density increasing from 0.52%to 3.13%.O-substitution will lead 1.08 eV larger bandgap?O atom density from 9.38%to 21.88%?.H-substitution has little influence.?2?Preparation of h-BN based on magnetron sputtering,characterization using FTIR,XPS and UV-Vis and optimization of sputtering parameters.The experiment results indicate that using N₂/H₂ can improve the quality of h-BN membranes.Also,the h-BN membranes have a bandgap of 5.76 eV and can remain stable for more than one year.?3?A new method of h-BN bandgap modulation.By reducing the content of N₂ in the working gas,the bandgap of h-BN membrane will increase from 4.97 eV to 5.76eV?absorption wave length 249.5-215.3 nm?,so the bandgap changes in range of 0.89eV,which makes the absorption band edge into solar-blind UV range.