Yoo Changyun, Sherwin Mark S, West Kenneth W, Pfeiffer Loren N, Kawamura Jonathan H, Karasik Boris S
Jet Propulsiton Laboratory, California Institute of Technology, Pasadena, CA, USA.
University of California, Santa Barbara, CA, USA.
Nanophotonics. 2024 Feb 5;13(10):1711-1723. doi: 10.1515/nanoph-2023-0752. eCollection 2024 Apr.
We investigate the THz intersubband absorption behavior of a single 40-nm wide GaAs/AlGaAs square quantum well (QW) using Johnson noise thermometry. In our measurements, the Johnson noise associated with intersubband absorption is measured from the in-plane conduction channel of the QW while its intersubband absorption behavior is being tuned through the independent control of the charge density and the perpendicular DC electric field. Our measurements enable the study of intersubband absorption of a small (∼20,000 and potentially fewer) number of electrons in a single mesoscopic device, as well as direct measurement of the electron heating from intersubband absorption. By measuring the Johnson noise response to monochromatic THz radiation at 2.52 THz and 4.25 THz at 20 K as a function of the DC electric field over a wide range of charge density, we show that the observed Johnson noise behavior correlates well with the expected intersubband absorption of the 40-nm QW. To explain the absorption features of the experimental results, we model the data by calculating the THz coupling efficiency based on the impedance model for intersubband absorption, which qualitatively reproduces the observed Johnson noise behavior well. Based on the temperature calibration of the Johnson noise measured at 2.52 THz, we deduce an increase in the electron temperature Δ of K when the maximum absorption of THz power occurs in the device.
我们使用约翰逊噪声测温法研究了单个40纳米宽的GaAs/AlGaAs方形量子阱（QW）的太赫兹子带间吸收行为。在我们的测量中，与子带间吸收相关的约翰逊噪声是从量子阱的面内传导通道测量的，同时通过独立控制电荷密度和垂直直流电场来调节其太赫兹子带间吸收行为。我们的测量能够研究单个介观器件中少量（约20,000个甚至可能更少）电子的子带间吸收，以及直接测量子带间吸收导致的电子加热。通过在20K温度下测量2.52太赫兹和4.25太赫兹的单色太赫兹辐射的约翰逊噪声响应，作为宽电荷密度范围内直流电场的函数，我们表明观察到的约翰逊噪声行为与40纳米量子阱预期的子带间吸收密切相关。为了解释实验结果的吸收特征，我们基于子带间吸收的阻抗模型通过计算太赫兹耦合效率对数据进行建模，定性地很好地再现了观察到的约翰逊噪声行为。基于在2.52太赫兹下测量的约翰逊噪声的温度校准，我们推断当器件中太赫兹功率出现最大吸收时，电子温度升高了 开尔文。
