透射式p型GaN(0001)光电阴极的表面洁净度及表征研究  

Influence of Etching and Cleaning on Surfaces of Transmission-Mode p-Type GaN(0001)Photocathode

作　　者：冯刘[1,2] 石峰[1,2] 苗壮[1,2] 程宏昌[1,2] 师宏立[1,2] 高翔[1,2] 王龙[1,2] 牛森[1,2] 

机构地区：[1]微光夜视技术重点实验室,西安710065 [2]北方夜视科技集团有限公司,昆明650223

出　　处：《真空科学与技术学报》2016年第1期10-14,共5页Chinese Journal of Vacuum Science and Technology

摘　　要：在p型GaN(0001)光电阴极的化学腐蚀和高温热清洗的处理过程中,为了评价化学处理和热清洗的效果,利用X射线光电子谱分析了不同阶段的光电阴极表面状况。结果表明,开始处理前,表面存在严重的C、O污染,C的表面覆盖率接近2个单原子层,而O稍小于1个单原子层,并且表面生成Ga_2O_3氧化层。经2:2:1的H_2SO_4:H_2O_2:H_2O混合溶液化学腐蚀处理后,C的表面覆盖率为0.36个单原子层,O的覆盖率为0.21个单原子层,化学腐蚀去除了大部分的C、O污染,露出了体材料。700℃高温热处理后,表面的C覆盖率低于百分之一个单原子层,而O的覆盖率也仅为0.07个单原子层,基本去除了C、O污染,并且表面Ga:N比为1.01:1,达到体材料的理想配比。GaN光电阴极在H_2SO_4/H_2O_2混合溶液中腐蚀15 min并在700℃下真空热清洗30min后,可以有效去除C、O污染和氧化物,获得洁净表面,进行Cs-O激活后可以获得负电子亲和势。The surfaces of the Mg-doped,p-type GaN（0001） thin films,synthesized by molecular beam chemical vapor deposition（MOCVD） on sapphire substrate,were cleaned by wet chemical etching and high temperature annealing in vacuum.The impact of the cleaning conditions,including but not limited to the mole fractions of the H2SO4：H2O2：H2O solution,etching time,annealing temperature and pressure,on the microstructures and stoichiometrics of the GaN coatings were investigated with X-ray photoelectron spectroscopy（XPS）.The results show that the high densities of C,O and Ga2O3contaminants on the as-deposited GaN surfaces can be completely removed by wet etching followed by vacuum annealing.To be specific,under the optimized cleaning conditions,the etching removed most impurities and the vacuum annealing completely removed the rest sub-monolayers of impurities,making the surface stoichiometrics equal to those of the bulk GaN material.

关 键 词：GAN X射线光电子谱 化学腐蚀 热清洗 覆盖率 

分 类 号：TH838.3[机械工程—仪器科学与技术]