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Université de Neuchâtel

InP-based quantum cascade detectors in the mid-infrared

Graf, Marcel ; Hoyler, Nicolas ; Giovannini, Marcella ; Faist, Jérôme ; Hofstetter, Daniel

In: Applied Physics Letters, 2006, vol. 88, no. 241118, p. 1-3

We present two InP-based quantum cascade detectors (QCDs) in the mid-infrared wavelength range. Their narrow band detection spectra are centered at 5.3 and 9 µm. A vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy, leads to 10 K responsivities R of 3.2 and 9.0 mA/W and background limited detectivities...

Université de Neuchâtel

Terahertz range quantum well infrared photodetector

Graf, Marcel ; Scalari, Giacomo ; Hofstetter, Daniel ; Faist, Jérôme ; Beere, Harvey ; Linfield, Edmund ; Ritchie, David ; Davies, Giles

In: Applied Physics Letters, 2004, vol. 84, p. 475-477

We demonstrated a GaAs/AlGaAs-based far-infrared quantum well infrared photodetector at a wavelength of λ=84 µm. The relevant intersubband transition is slightly diagonal with a dipole matrix element of 3.0 nm. At 10 K, a responsivity of 8.6 mA/W and a detectivity of 5×107 cm √Hz/W have been achieved; and successful detection up to a device temperature of 50 K has been...

Université de Neuchâtel

Microsecond time scale lateral-mode dynamics in a narrow stripe InGaN laser

Eichler, Christoph ; Hofstetter, Daniel ; Chow, Weng W. ; Miller, Stephan ; Weimar, Andreas ; Lell, Alfred ; Härle, Volker

In: Applied Physics Letters, 2004, vol. 84, p. 2473-2475

Time-resolved measurements of the spectrum and the far field of InGaN-based laser diodes show lateral-mode changes and gradual tilting of the far field on a microsecond time scale. Numerical simulations based on a microscopic theory are in good agreement with the measurements. The observed effects are attributed to lateral carrier diffusion in combination with thermal lensing.

Université de Neuchâtel

Terahertz intersubband emission in strong magnetic fields

Blaser, Stéphane ; Rochat, Michel ; Beck, Mattias ; Hofstetter, Daniel ; Faist, Jérôme

In: Applied Physics Letters, 2002, vol. 81, p. 67-69

Electroluminescence in quantum-cascade structures based on vertical transitions is studied in a strong perpendicular magnetic field in the limit in which the cyclotron energy is larger than the intersubband transition energy. Cyclotron emission and a luminescence intensity enhancement up to a factor of 6 is observed in GaAs/AlGaAs and InGaAs/InAlAs vertical transition-based quantum-cascade...

Université de Neuchâtel

Continuous-wave distributed-feedback quantum-cascade lasers on a Peltier cooler

Aellen, Thierry ; Blaser, Stéphane ; Beck, Mattias ; Hofstetter, Daniel ; Faist, Jérôme ; Gini Emilio

In: Applied Physics Letters, 2003, vol. 83, p. 1929-1931

Continuous-wave operation of λ~9 µm distributed-feedback quantum-cascade lasers is reported up to a temperature of 260 K. Single-frequency emission with a side mode suppression ratio of ≥27 dB and with a tuning range of 5 cm–1 between 200 and 245 K (a tunability of –0.078 cm–1/K and –0.764 cm–1/W) is obtained for the junction-down mounted...

Université de Neuchâtel

16.5 µm quantum cascade detector using miniband transport

Giorgetta, Fabrizio R. ; Baumann, Esther ; Graf, Marcel ; Ajili, Lassaad ; Hoyler, Nicolas ; Marcella Giovannini ; Faist, Jérôme ; Hofstetter, Daniel ; Krötz, Peter ; Sonnabend, Guido

In: Applied Physics Letters, 2007, vol. 90, no. 231111, p. 1-3

The authors report on an InP based photovoltaic quantum cascade detector operating at 16.5 µm and using miniband-based vertical transport. This concept allowed the construction of a longitudinal optical phonon extraction stair with two rungs without touching on a high device resistance. At 10 K, they observed a responsivity of 1.72 mA/W and a Johnson noise limited detectivity of 2.2×109...

Université de Neuchâtel

Short wavelength (4 µm) quantum cascade detector based on strain compensated InGaAs/InAlAs

Giorgetta, Fabrizio R. ; Baumann, Esther ; Théron, Ricardo ; Pellaton, M. L. ; Hofstetter, Daniel ; Fischer, M. ; Faist, Jérôme

In: Applied Physics Letters, 2008, vol. 92, no. 121101, p. 1-3

We report on a quantum cascade detector based on nearly strain compensated InGaAs/InAlAs pseudomorphically grown on InP substrate and detecting light at short wavelengths around 4 µm. The background limited infrared performance (BLIP) condition is met at a temperature of 108 K with a high detectivity of D*BLIP =1.2×1011 Jones.

Université de Neuchâtel

Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

Wang, Z. ; Reimann, K. ; Woerner, M. ; Elsaesser, T. ; Hofstetter, Daniel ; Hwang, J. ; Schaff, William J. ; Eastman, L. F.

In: Physical Review Letters, 2005, vol. 94, no. 037403, p. 1-4

We present the first evidence for a distinct optical phonon progression in the linear and nonlinear intersubband absorption spectra of electrons in a GaN/Al0.8Ga0.2N heterostructure. Femtosecond two-color pump-probe experiments in the midinfrared reveal spectral holes on different vibronic transitions separated by the LO-phonon frequency. These features wash out with a decay...

Université de Neuchâtel

Structural investigations of epitaxial InN by x-ray photoelectron diffraction and x-ray diffraction

Hofstetter, Daniel ; Despont, Laurent ; Garnier, Michael Bernard Gunnar ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Aebi, Philipp ; Kirste, Lutz ; Lu, Hai ; Schaff, William J.

In: Applied Physics Letters, 2007, vol. 90, no. 191912, p. 1-3

The authors investigated a 1 µm thick molecular beam epitaxy–grown InN film by means of full hemispherical x-ray photoelectron diffraction and high resolution x-ray diffraction. While x-ray diffraction reveals that this nominally hexagonal InN layer contains roughly 1% of cubic phase InN, a comparison between measured and simulated x-ray photoelectron diffraction data allowed them to...