多层AlGaAs的时间分辨归一化反射率及各向异性反射率谱在线监测及分析

In Situ Monitoring and Analysis of Normalized Reflectance and Reflectance Anisotropy of Multilayer AlGaAs Structure

通过光学在线监测技术对多层AlxGa1-xAs样品生长过程中的生长速率与表面结构进行了分析。描述了选取合适探测光子能量的方法并在线监测了样品生长过程中表面归一化反射率(Normalized Reflectance,NR)和各向异性反射率(Reflectance Anisotropy,RA)随生长时间的变化,得到了样品的时间分辨NR及RA曲线,利用光学干涉原理解释了NR曲线的振荡衰减特性。不同AlxGa1-xAs层NR曲线收敛值随Al组分的单调变化被认为是材料的折射率变化引起的,而RA值随Al组分的增加而增加说明Al原子的并入对表面光学各向异性有影响。通过拟合每一层材料的归一化反射谱振荡曲线得到了各层生长速率,与扫描电镜测试结果差别小于0.02 nm/s。对时间分辨RA曲线分析发现,生长温度对GaAs表面原子结构产生了影响。

The growth rate and surface structure of AlGaAs sample were investigated by employing the optical in-situ monitoring technique.In situ monitoring of optical time resolved normalized reflectance（NR） and reflectance anisotropy（RA） in growth process of multilayer AlxGa1-xAs sample was carried out.Oscillation characteristics of NR curve was analyzed.Converged value of NR and RA curve changed monotonously with Al composition at the monitoring optical energy of 1.9 eV.The growth rate was gained from fitting the NR transient.And the deviation of calculated growth rate was lower than 0.02 nm/s compared to the SEM measurement results.From the analysis of time resolved RA curve,surface reconstruction caused by the growth temperature was observed during the epi-growth of GaAs layers.