Quantum well (QW) heterostructures have been extensively used for the realization of a wide range of optical and electronic devices. Exploiting their potential for further improvement and development requires a fundamental understanding of their electronic structure. So far, the most commonly used experimental techniques for this purpose have been all-optical spectroscopy methods that, however, are generally averaging in momentum space. Additional information can be gained by angle-resolved photoelectron spectroscopy (ARPES), which measures the electronic structure with momentum resolution. Here we report on the use of extremely low-energy ARPES (photon energy ~ 7 eV) to increase depth sensitivity and access buried QW states, located at 3 nm and 6 nm below the surface of cubic-GaN/AlN and GaAs/AlGaAs heterostructures, respectively. We find that the QW states in cubic-GaN/AlN can indeed be observed, but not their energy dispersion, because of the high surface roughness. The GaAs/AlGaAs QW states, on the other hand, are buried too deep to be detected by extremely low-energy ARPES. Since the sample surface is much flatter, the ARPES spectra of the GaAs/AlGaAs show distinct features in momentum space, which can be reconducted to the band structure of the topmost surface layer of the QW structure. Our results provide important information about the samples’ properties required to perform extremely low-energy ARPES experiments on electronic states buried in semiconductor heterostructures.

量子阱 (QW) 异质结构已广泛用于实现各种光学和电子器件。开发它们的潜力以进一步改进和发展需要对它们的电子结构有一个基本的了解。到目前为止，为此目的最常用的实验技术是全光学光谱方法，然而，这些方法通常在动量空间中进行平均。额外的信息可以通过角分辨光电子能谱 (ARPES) 获得，它以动量分辨率测量电子结构。在这里，我们报告了使用极低能量 ARPES（光子能量 ~ 7 eV）来增加深度灵敏度并访问位于立方 GaN/AlN 和 GaAs/AlGaAs 异质结构表面下方 3 nm 和 6 nm 处的掩埋 QW 状态， 分别。我们发现立方GaN/AlN中的QW状态确实可以观察到，但由于表面粗糙度高，所以不能观察到它们的能量色散。另一方面，GaAs/AlGaAs QW 状态埋藏得太深，无法被极低能量的 ARPES 检测到。由于样品表面更平坦，GaAs/AlGaAs 的 ARPES 光谱在动量空间中表现出明显的特征，可以将其重新传导到 QW 结构的最顶层表层的能带结构。我们的结果提供了有关对埋在半导体异质结构中的电子态进行极低能量 ARPES 实验所需的样品特性的重要信息。被埋得太深，无法被极低能量的 ARPES 探测到。由于样品表面更平坦，GaAs/AlGaAs 的 ARPES 光谱在动量空间中表现出明显的特征，可以将其重新传导到 QW 结构的最顶层表层的能带结构。我们的结果提供了有关对埋在半导体异质结构中的电子态进行极低能量 ARPES 实验所需的样品特性的重要信息。被埋得太深，无法被极低能量的 ARPES 探测到。由于样品表面更平坦，GaAs/AlGaAs 的 ARPES 光谱在动量空间中表现出明显的特征，可以将其重新传导到 QW 结构的最顶层表层的能带结构。我们的结果提供了有关对埋在半导体异质结构中的电子态进行极低能量 ARPES 实验所需的样品特性的重要信息。