Probing THz intersubband absorption using Johnson noise thermometry

Changyun Yoo, Mark S. Sherwin, Kenneth W. West, Loren N. Pfeiffer, Jonathan H. Kawamura, Boris S. Karasik

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


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 2.52THz and 4.25THz at 20K 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 2.52THz, we deduce an increase in the electron temperature ΔT e of ∼ 35 ${\sim} 35$ K when the maximum absorption of THz power occurs in the device.

Original languageEnglish (US)
Pages (from-to)1711-1723
Number of pages13
Issue number10
StatePublished - Apr 3 2024

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


  • Johnson noise thermometry
  • THz intersubband transitions
  • Tunable Antenna-Coupled Intersubband Terahertz (TACIT) mixer


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