[Zurück]

M Giparakis, H. Knötig, M Beiser, J. Hillbrand, H. Detz, W. Schrenk, B. Schwarz, G. Strasser, A. M. Andrews:
"2.7 μm short-wavelength InAs/AlAsSb quantum cascade detector";
Poster: Online Conference International Quantum Cascade Laser School & Workshop (IQCLSW 2020), Zürich; 07.09.2020 - 10.09.2020; in: "Proc. International Quantum Cascade Lasers School & Workshop", (2020).

Quantum cascade detectors (QCDs) are unipolar intersubband devices, which operate as photovoltaic detectors at room-temperature. The light is detected via optical transitions between two bound levels in a superlattice-like heterostructure in the mid- and far-infrared spectral region [1].
InAs/AlAs0.16Sb0.84 has potential for short wavelength mid-infrared QCDs [2]. This material system has the largest conduction band offset in nonpolar III-V semiconductors of 2.1 eV. Furthermore, InAs has a low effective electron mass of 0.023 𝑚 , which leads to high electron mobility. The 𝑚 is beneficial for low intersubband scattering and should allow for the design of devices with increased total absorption and reduced noise. On the other hand, InAs has a narrow bandgap of 0.35 eV, which would imply an absorption of the InAs substrate at wavelengths below 3.54 µm.
In the present work we present a QCD grown with the lattice-matched InAs/AlAs0.16Sb0.84 material system on an InAs substrate using molecular beam epitaxy that shows an absorption wavelength of 2.7 µm. This corresponds to an energy of 0.459 eV which lies above the bandgap of the InAs substrate. The absorption at the target wavelength is made possible through the band structure design. The light is absorbed through a vertical transition from the ground level to the upper state in the active region. The excited electrons are then extracted to the next ground level via a longitudinal-optical phonon assisted extraction. Short-period superlattice contacts before and after the active region provide good electrical transport.
The grown sample was processed into mesa devices by wet-chemical etching and deposition of TiAu contacts. The absorption spectrum was obtained at room-temperature using a Fourier-transform infrared spectrometer with a broadband mid-infrared Globar source and a long-pass filter with a cut-off wavelength of 2.5 µm. The sample was cleaved through the mesas and the light was coupled into the detectors through the facet.

References:

[1] A. Harrer et al., "4.3 μm quantum cascade detector in pixel configuration," Optics Express 24, No. 15, 17043 (2016).
[2] P. Reininger et al., "InAs/AlAsSb based quantum cascade detector," Applied Physics Letters 107, 081107 (2015).

https://publik.tuwien.ac.at/files/publik_290680.pdf