Supplementary material: Comment on Infrared dielectric function of GaAs1-xPx semiconductor alloys near the reststrahlen bands [Appl. Phys. Lett. 123, 172102 (2023)]

In the main text, we outline an updated version of the PM for GaAs(1-x)P(x) that explains, beyond existing CM and PM approaches, its phonon mode behavior, as apparent in the novel IR-ellipsometry Im{εr (ω,x)} data of Zollner et al. (Fig. S1, symbols). Sec. I reports on the main features of the cluster model (CM) and of the percolation model (PM). A common terminology is introduced to facilitate the discussion. Both the TO-frequency and the TO-intensity aspects are covered. In Sec. II, an updated version of the PM for GaAs(1-x)P(x) is presented (Fig. S2), supported by existing (Fig. S3) and novel (Fig. S4) ab initio phonon calculations at minimum (x~0,1 - TO-frequency aspect) and maximum (x~0.5 - TO-intensity aspect) alloy disorder. This updated PM scheme for GaAs(1-x)P(x) is directly confronted with Zollner's Im{εr (ω,x)} experimental data (Fig. S1, curves). An overview of the so far tested CM and PM approaches on GaAs(1-x)P(x), including the current PM one, helps to evaluate their relative bias and merits. The overview focuses on the sensitive Ga-P phonon signal at the critical GaAs0.725P0.275 composition (Fig. S5), used as a case study. Last, for the sake of completeness, we show how the latter signal is impacted within the PM by deviating from the ideal random As↔P substitution (Fig. S6).

在正文部分，我们概述了一种针对 GaAs(1-x)P(x) 的更新版 PM 模型，该模型不仅超越了现有的 CM 和 PM 方法，还阐释了其声子模式行为，这一行为在 Zollner 等人新颖的 IR-椭偏仪数据 Im{εr (ω,x)}（图 S1，符号）中表现得尤为明显。第 I 节报告了簇模型（CM）和渗透模型（PM）的主要特征，并引入了通用术语以促进讨论。涵盖了 TO 频率和 TO 强度两个方面。在第 II 节中，我们提出了针对 GaAs(1-x)P(x) 的 PM 更新版（图 S2），该版本得到了现有（图 S3）和新型（图 S4）的从头算声子计算的支持，这些计算在最小（x~0,1 - TO 频率方面）和最大（x~0.5 - TO 强度方面）合金无序度下进行。针对 GaAs(1-x)P(x) 的此更新 PM 方案直接与 Zollner 的 Im{εr (ω,x)} 实验数据（图 S1，曲线）进行了对比。对迄今为止在 GaAs(1-x)P(x) 上测试过的 CM 和 PM 方法（包括当前的 PM 方法）的概述有助于评估它们的相对偏差和优点。概述重点在于敏感的 Ga-P 声子信号，该信号在关键的 GaAs0.725P0.275 组成（图 S5）中得以体现，并作为案例研究。最后，为了全面起见，我们展示了当偏离理想的随机 As↔P 替代时，后者信号如何在 PM 中受到影响（图 S6）。