Doping And Electrical Properties Of Hexagonal Boron Nitride Thin Films Prepared By RF Magnetron Sputtering Method

Hexagonal boron nitride（h-BN）is a kind of synthetic ultra-wide-band gap material with a bandgap of about 5.97 e V.Together with traditional wide-band gap semiconductor materials,it forms the basis of semiconductor technology and shows great potential in high power and high temperature electronic devices as well as sensing and quantum applications.However,due to the difficulty in the preparation of h-BN,it is challenging to obtain high quality and large area continuous h-BN.In addition,the deep-level defects of h-BN lead to low doping efficiency,which greatly limits its application in the field of electronics and optoelectronic devices.Therefore,it is very necessary to find an appropriate method to prepare high quality and large area h-BN thin film with high doping efficiency.Based on this,this paper adopts the method of radio frequency magnetron sputtering to grow h-BN thin films,and doping the samples through in-situ doping and surface transfer doping.The research results are as follows:（1）In-situ Si/O co-doping of h-BN thin films.The n-type conductivity of h-BN film is enhanced by adding Si and O in the deposition process by radio frequency magnetron sputtering method.The resultant h-BN films are about 50 nm thick and contain nitrogen vacancy（V_N）defects.The addition of O and Si can effectively heal V_N defects and significantly reduce the resistivity of h-BN films.The results of X-ray photoelectron spectroscopy show that under B-rich conditions,the O substituted V_Nbond with B leads to the formation of Si-N bond,which plays an important role in the n-type conductivity of h-BN films.Compared with undoped samples,the resistivity of h-BN film after doping is reduced by 5 to 6 orders of magnitude.The variable temperature resistivity test results show that there are two shallow donor energy levels with activation energies of 130 me V at room temperature（300-380 K）and 520 me V at higher temperatures（380-470 K）.The n-h-BN/p-Si heterojunctions exhibit obvious rectification characteristics at room temperature,in which tunneling behavior dominates the whole injection regimes due to effective carrier doping.（2）Surface charge transfer doping h-BN thin films.The surface charge transfer doping of heteroepitaxial h-BN thin film has been achieved by using molybdenum trioxide（Mo O₃）and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane（F4-TCNQ）as surface dopants.After the addition of surface dopants,the h-BN film shows the increase of the surface current,which increases the surface current of the h-BN film by up to 6 orders of magnitude.The experimental results of this thesis shows the effectiveness of co-doping of Si and O and surface charge transfer doping for improving the doping efficiency,and provides possible routes for the application of h-BN in the field of electronics,optoelectronics and photovoltaic in the future.