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Lähnemann J, Browne DA, Ajay A, Jeannin M, Vasanelli A, Thomassin JL, Bellet-Amalric E, Monroy E. Near- and mid-infrared intersubband absorption in top-down GaN/AlN nano- and micro-pillars. NANOTECHNOLOGY 2019; 30:054002. [PMID: 30500783 DOI: 10.1088/1361-6528/aaef72] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present a systematic study of top-down processed GaN/AlN heterostructures for intersubband optoelectronic applications. Samples containing quantum well superlattices that display either near- or mid-infrared intersubband absorption were etched into nano- and micro-pillar arrays in an inductively coupled plasma. We investigate the influence of this process on the structure and strain-state, on the interband emission and on the intersubband absorption. Notably, for pillar spacings significantly smaller (≤1/3) than the intersubband wavelength, the magnitude of the intersubband absorption is not reduced even when 90% of the material is etched away and a similar linewidth is obtained. The same holds for the interband emission. In contrast, for pillar spacings on the order of the intersubband absorption wavelength, the intersubband absorption is masked by refraction effects and photonic crystal modes. The presented results are a first step towards micro- and nano-structured group-III nitride devices relying on intersubband transitions.
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Affiliation(s)
- Jonas Lähnemann
- Université Grenoble-Alpes, CEA, INAC, PHELIQS, 17 av. des Martyrs, F-38000, Grenoble, France. Paul-Drude-Institut für Festkörperelektronik, Leibniz Institut im Forschugnsverbund Berlin e.V., Hausvogteiplatz 5-7, D-10117, Berlin, Germany
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Burnett BA, Williams BS. Design strategy for terahertz quantum dot cascade lasers. OPTICS EXPRESS 2016; 24:25471-25481. [PMID: 27828485 DOI: 10.1364/oe.24.025471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The development of quantum dot cascade lasers has been proposed as a path to obtain terahertz semiconductor lasers that operate at room temperature. The expected benefit is due to the suppression of nonradiative electron-phonon scattering and reduced dephasing that accompanies discretization of the electronic energy spectrum. We present numerical modeling which predicts that simple scaling of conventional quantum well based designs to the quantum dot regime will likely fail due to electrical instability associated with high-field domain formation. A design strategy adapted for terahertz quantum dot cascade lasers is presented which avoids these problems. Counterintuitively, this involves the resonant depopulation of the laser's upper state with the LO-phonon energy. The strategy is tested theoretically using a density matrix model of transport and gain, which predicts sufficient gain for lasing at stable operating points. Finally, the effect of quantum dot size inhomogeneity on the optical lineshape is explored, suggesting that the design concept is robust to a moderate amount of statistical variation.
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Rey BM, Elnathan R, Ditcovski R, Geisel K, Zanini M, Fernandez-Rodriguez MA, Naik VV, Frutiger A, Richtering W, Ellenbogen T, Voelcker NH, Isa L. Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating. NANO LETTERS 2016; 16:157-63. [PMID: 26672801 DOI: 10.1021/acs.nanolett.5b03414] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.
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Affiliation(s)
- By Marcel Rey
- Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
| | - Roey Elnathan
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries Institute, University of South Australia , Mawson Lakes, 5095, Australia
| | - Ran Ditcovski
- Department of Physical Electronics, Fleischman Faculty of Engineering, Tel-Aviv University , Tel-Aviv 69978, Israel
| | - Karen Geisel
- Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, 52056, Aachen, Germany
| | - Michele Zanini
- Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
| | - Miguel-Angel Fernandez-Rodriguez
- Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
- Biocolloid and Fluid Physics Group, Applied Physics, University of Granada , 18071 Granada, Spain
| | - Vikrant V Naik
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
| | - Andreas Frutiger
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich , Gloriastrasse 35, ETZ F76, CH-8092 Zurich, Switzerland
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, 52056, Aachen, Germany
| | - Tal Ellenbogen
- Department of Physical Electronics, Fleischman Faculty of Engineering, Tel-Aviv University , Tel-Aviv 69978, Israel
| | - Nicolas H Voelcker
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries Institute, University of South Australia , Mawson Lakes, 5095, Australia
| | - Lucio Isa
- Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
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Beeler M, Hille P, Schörmann J, Teubert J, de la Mata M, Arbiol J, Eickhoff M, Monroy E. Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures. NANO LETTERS 2014; 14:1665-1673. [PMID: 24502703 DOI: 10.1021/nl5002247] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report the observation of transverse-magnetic-polarized infrared absorption assigned to the s-p(z) intraband transition in Ge-doped GaN/AlN nanodisks (NDs) in self-assembled GaN nanowires (NWs). The s-p(z) absorption line experiences a blue shift with increasing ND Ge concentration and a red shift with increasing ND thickness. The experimental results in terms of interband and intraband spectroscopy are compared to theoretical calculations of the band diagram and electronic structure of GaN/AlN heterostructured NWs, accounting for their three-dimensional strain distribution and the presence of surface states. From the theoretical analysis, we conclude that the formation of an AlN shell during the heterostructure growth applies a uniaxial compressive strain which blue shifts the interband optical transitions but has little influence on the intraband transitions. The presence of surface states with density levels expected for m-GaN plane charge-deplete the base of the NWs but is insufficient to screen the polarization-induced internal electric field in the heterostructures. Simulations show that the free-carrier screening of the polarization-induced internal electric field in the NDs is critical to predicting the photoluminescence behavior. The intraband transitions, on the other hand, are blue-shifted due to many-body effects, namely, the exchange interaction and depolarization shift, which exceed the red shift induced by carrier screening.
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Affiliation(s)
- M Beeler
- CEA-CNRS Group Nanophysics and Semiconductors, CEA/INAC/SP2M and CNRS-Institute Néel, 17 rue des Martyrs, 38054 Grenoble cedex 9, France
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Krall M, Brandstetter M, Deutsch C, Detz H, Andrews AM, Schrenk W, Strasser G, Unterrainer K. Subwavelength micropillar array terahertz lasers. OPTICS EXPRESS 2014; 22:274-282. [PMID: 24514988 DOI: 10.1364/oe.22.000274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report on micropillar-based terahertz lasers with active pillars that are much smaller than the emission wavelength. These micropillar array lasers correspond to scaled-down band-edge photonic crystal lasers forming an active photonic metamaterial. In contrast to photonic crystal lasers which use significantly larger pillar structures, lasing emission is not observed close to high-symmetry points in the photonic band diagram, but in the effective medium regime. We measure stimulated emission at 4 THz for micropillar array lasers with pillar diameters of 5 µm. Our results not only demonstrate the integration of active subwavelength optics in a terahertz laser, but are also an important step towards the realization of nanowire-based terahertz lasers.
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