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End date: 2024 × Start date: 2020 × DDC: 530 × Subject: Gallium arsenide × Subject: III-V semiconductors ×

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Now showing 1 - 3 of 3
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    Infrared emission bands and thermal effects for 440-nm-emitting GaN-based laser diodes
    (New York, NY : American Institute of Physics Inc., 2020) Mao F.; Hong J.; Wang H.; Chen Y.; Jing C.; Yang P.; Tomm J.W.; Chu J.; Yue F.
    Broad emission bands due to defects in (In,Ga,Al)N laser diodes operating at 440 nm are investigated using continuous-wave and pulsed currents. In addition to known yellow-green and short-wave infrared bands, defect emissions were observed even in the medium-wave infrared range. A separation from thermal radiation is possible. When using pulsed currents, a super-linearly increasing emission occurs at ∼1150 nm, which could be attributed to amplified spontaneous emission mainly due to the electroluminescence of deep defects in the optically active region. These results may be useful in interpreting the output power bottleneck of GaN-based lasers compared to mature GaAs-based lasers. © 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/1.5143802
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    Long-term stability of GaAs/AlAs terahertz quantum-cascade lasers
    (New York, NY : American Inst. of Physics, 2022) Schrottke, L.; Lü, X.; Biermann, K.; Gellie, P.; Grahn, H.T.
    We have investigated high-performance GaAs/AlAs terahertz (THz) quantum-cascade lasers (QCLs) with respect to the long-term stability of their operating parameters. The output power of lasers that contain an additional, thick AlAs refractive-index contrast layer underneath the cascade structure decreases after three months by about 35%. The deterioration of these lasers is attributed to the oxidation processes in this contrast layer starting from the facets. However, GaAs/AlAs THz QCLs with an Al0.9Ga0.1As refractive-index contrast layer exhibit long-term stability of the operating parameters over many years even when they are exposed to atmospheric conditions. Therefore, these lasers are promising high-power radiation sources in the terahertz spectral region for commercial applications.
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    Two-color two-dimensional terahertz spectroscopy: A new approach for exploring even-order nonlinearities in the nonperturbative regime
    (Melville, NY : American Institute of Physics, 2021) Woerner, Michael; Ghalgaoui, Ahmed; Reimann, Klaus; Elsaesser, Thomas
    Nonlinear two-dimensional terahertz (2D-THz) spectroscopy at frequencies of the emitted THz signal different from the driving frequencies allows for exploring the regime of (off-)resonant even-order nonlinearities in condensed matter. To demonstrate the potential of this method, we study two phenomena in the nonlinear THz response of bulk GaAs: (i) The nonlinear THz response to a pair of femtosecond near-infrared pulses unravels novel fourth- and sixth-order contributions involving interband shift currents, Raman-like excitations of transverse-optical phonon and intervalence-band coherences. (ii) Transient interband tunneling of electrons driven by ultrashort mid-infrared pulses can be effectively controlled by a low-frequency THz field with amplitudes below 50 kV/cm. The THz field controls the electron–hole separation modifying decoherence and the irreversibility of carrier generation.