We demonstrate terahertz intersubband absorptions in nitride step quantum wells (SQWs) grown by metal organic vapor phase epitaxy simultaneously on two different substrate orientations [Si(111) and Si(110)]. The structure of the SQWs consists of a 3 nm thick Al0.1Ga0.9N barrier, a 3 nm thick GaN well, and an Al0.05Ga0.95N step barrier with various thicknesses. This structure design has been optimized to approach a flatband potential in the wells to allow for an intersubband absorption in the terahertz frequency range and to maximize the optical dipole moment. Structural characterizations prove the high quality of the samples. Intersubband absorptions at frequencies of 5.6 THz (λ ≈ 54 μm), 7 THz (43 μm), and 8.9 THz (34 μm) are observed at 77 K on both substrate orientations. The observed absorption frequencies are in excellent agreement with calculations accounting for the depolarization shift induced by the electron concentration in the wells.We demonstrate terahertz intersubband absorptions in nitride step quantum wells (SQWs) grown by metal organic vapor phase epitaxy simultaneously on two different substrate orientations [Si(111) and Si(110)]. The structure of the SQWs consists of a 3 nm thick Al0.1Ga0.9N barrier, a 3 nm thick GaN well, and an Al0.05Ga0.95N step barrier with various thicknesses. This structure design has been optimized to approach a flatband potential in the wells to allow for an intersubband absorption in the terahertz frequency range and to maximize the optical dipole moment. Structural characterizations prove the high quality of the samples. Intersubband absorptions at frequencies of 5.6 THz (λ ≈ 54 μm), 7 THz (43 μm), and 8.9 THz (34 μm) are observed at 77 K on both substrate orientations. The observed absorption frequencies are in excellent agreement with calculations accounting for the depolarization shift induced by the electron concentration in the wells.

中文翻译：

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通过 MOVPE 在 Si(111) 和 Si(110) 衬底上生长的 GaN/AlGaN 阶梯量子阱的太赫兹子带间吸收

我们展示了通过金属有机气相外延在两种不同衬底方向上同时生长的氮化物阶梯量子阱 (SQW) 中的太赫兹子带间吸收 [Si(111) 和 Si(110)]。SQW 的结构由 3 nm 厚的 Al0.1Ga0.9N 势垒、3 nm 厚的 GaN 阱和不同厚度的 Al0.05Ga0.95N 阶梯势垒组成。这种结构设计已经过优化，以接近井中的平带电位，以允许太赫兹频率范围内的子带间吸收并最大化光学偶极矩。结构表征证明了样品的高质量。在 77 K 的两个衬底方向上观察到频率为 5.6 THz (λ ≈ 54 μm)、7 THz (43 μm) 和 8.9 THz (34 μm) 的子带间吸收。观察到的吸收频率与计算井中电子浓度引起的去极化偏移的计算非常一致。 我们证明了在两个不同的衬底方向上通过金属有机气相外延同时生长的氮化物阶梯量子阱 (SQW) 中的太赫兹子带间吸收[Si(111) 和 Si(110)]。SQW 的结构由 3 nm 厚的 Al0.1Ga0.9N 势垒、3 nm 厚的 GaN 阱和不同厚度的 Al0.05Ga0.95N 阶梯势垒组成。这种结构设计已经过优化，以接近井中的平带电位，以允许太赫兹频率范围内的子带间吸收并最大化光学偶极矩。结构表征证明了样品的高质量。频率为 5 的子带间吸收。6 THz (λ ≈ 54 μm)、7 THz (43 μm) 和 8.9 THz (34 μm) 在 77 K 时在两个衬底方向上均观察到。观察到的吸收频率与计算井中电子浓度引起的去极化偏移的计算非常一致。