First principles calculation of optical spectra of GaAs growing surface structures

我们发展了计算反射差谱（RDS）的方法，并从光学角度阐明了生长中的半导体表面和界面的电子结构。光谱起源与局域场效应；当电子态在表面/界面附近局域化（扩展）时，表面态（体态）之间的光学跃迁产生峰形（epsilon_2-导数形）光谱。从各种层厚计算中，显示出局部场对光谱有大约50个贡献。（001）阴离子表面；表面阴离子二聚体原子的悬键态在GaAs和ZnSe表面光谱中产生大峰结构。随着二聚体距离的减小，峰的位置和宽度分别增加了0.77eV/和0.5eV/，这很好地解释了Kobayashi等人最近的实验。（001）阳离子表面；顶层的阳离子原子通过产生sp^2/sp…更多的成键来稳定，从而支撑了垂直于表面的第二层阴离子的悬键状态。从这种状态到导带状态的光学跃迁产生了特征峰结构，这一特征对于ZnSe表面来说尤为显著。吸附（001）表面和界面；根据吸附原子的轨道能量和GaAs波段之间的相对能量位置，GaAs表面的光谱强度为Sb>P>N数量级。当异质外延原子层厚度大于5时，界面光谱呈现出epsilon_2-导数形状，这一结果解释了Yasuda等人最近对ZnSe/GaAs界面的实验结果。（110）非极性砷化镓表面；As和Ga的悬键态和Ga-As表面键的反键态之间的光学跃迁产生了大峰，反映了屈曲重构，这些结果可以用来确定生长时的吸附位置。少

We have developed the method to calculate the reflectance difference spectra (RDS) and clarified the electronic structures of growing semiconductor surfaces and interfaces from optical viewpoints as follows.1.Spectra origin and local field effect ; when the electronic states are localized (extended) around the surface/interface, the optical transitions between surface states (bulk states) produce peak-shaped (epsilon_2-derivative-shaped) spectra. From the various layr-thickness calculations, the local field is shown having about 50 contributions to the spectra.2.(001) anion surfaces ; the dangling-bond states of surface anion-dimer atoms produce the large peak structures in GaAs and ZnSe surface spectra. The peak position and width respectively increase by 0.77eV/ and 0.5eV/ with decreasing the dimer distance, which well explains the recent experiments by Kobayashi et al.3.(001) cation surfaces ; the cation atoms on the top layr largely sink into bulks to stabilize by producing sp^2/sp … More bonding, which stands up the dangling-bond states of the second-top-layr anions perpendicular to the surface. The optical transition from such states to the conduction-band states produces the characteristic peak structures, which feature is particularly remarkable for ZnSe surfaces.4.Adsorbed (001) surfaces and interfaces ; depending on the relative energy position between GaAs bands and orbital energies of adsorbed atoms, the spectra intensity has the order of Sb>P>N for GaAs surfaces. When the thickness of hetero-epitaxialized atomic layrs is more than five, the interface spectra show the epsilon_2-derivative shape, which results explain the recent experiments of ZnSe/GaAs interfaces by Yasuda et al.5.(110) nonpolar GaAs surfaces ; reflecting the buckling reconstructions, the optical transitions between the dangling-bond states of As and Ga and the anti-bonding states of Ga-As surface bonds produce the large peaks, which results can be used to determine the adsorption sites on growth. Less