Abstract Photoreflectance and ellipsometry are two very useful optical spectroscopy techniques employed to analyze the electronic band structure of semiconductors. Photoreflectance and ellipsometry spectra of gallium arsenide nitride (GaNAs) thin films on gallium arsenide (GaAs) layers may be composed of transitions from the conduction bands of the alloy and the binary (E-, E+, and E0, respectively) in conjunction with their interaction spin-orbit split-off valence band (E-+Δ0 and E0+Δ0). For low concentration of nitrogen (between 0.2 and 0.6 %), the determination of the E+ conduction band becomes difficult to distinguish by the fact that critical points are superimposed in the spectrum of both characterization techniques. In this work, a method to determine the E+ conduction band of GaNAs thin films grown on GaAs by molecular beam epitaxy is proposed when the overlapping of spectral features influences their optical determination. When using spectroscopic characterization techniques, the modulation/excitation region depends on the wavelength employed and sample characteristics, and consequently low nitrogen concentration in the alloy in conjunction with the thickness of the GaNAs layers have been found responsible for the signal overlapping. It is demonstrated that by decreasing the sample temperature in the photoreflectance process the overlapping is avoided, allowing for a correct interpretation of the GaNAs conduction band splitting analysis and discarding the contribution of built-in electric fields. From these results, we achieved a precise experimental determination of the presence/absence of the band splitting predicted by the band anti-crossing model using non-destructive characterization tools.

中文翻译：

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分子束外延生长的GaNs薄膜光学跃迁的重叠效应

摘要 光反射和椭偏法是两种非常有用的光谱技术，用于分析半导体的电子能带结构。砷化镓 (GaAs) 层上的氮化砷化镓 (GaNAs) 薄膜的光反射率和椭偏光谱可能由合金和二元（分别为 E-、E+ 和 E0）导带的跃迁以及它们的相互作用自旋轨道分裂价带（E-+Δ0 和 E0+Δ0）。对于低浓度氮（0.2% 和 0.6% 之间），E+ 导带的确定变得难以区分，因为临界点叠加在两种表征技术的光谱中。在这项工作中，当光谱特征的重叠影响其光学测定时，提出了一种通过分子束外延法测定生长在 GaAs 上的 GaNAs 薄膜的 E+ 导带的方法。当使用光谱表征技术时，调制/激发区域取决于所使用的波长和样品特性，因此发现合金中的低氮浓度与 GaNAs 层的厚度是信号重叠的原因。结果表明，通过降低光反射过程中的样品温度，避免了重叠，从而可以正确解释 GaNAs 导带分裂分析并丢弃内置电场的贡献。从这些结果来看，