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  • 1
    Electronic Resource
    Electronic Resource
    Ballistic transport through GaAs–AlGaAs superlattices in transverse magnetic fields (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3495-3500 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, ballistic electron transport through the lowest miniband of a biased GaAs–AlGaAs superlattice is investigated in transverse magnetic fields. As method we employ a solid-state version of ballistic electron emission microscopy/spectroscopy using a metal-insulator-metal injector structure that replaces the tip of the scanning tunneling microscope (STM). The ballistic electron current measured as a function of the collector bias shows a peak at flatband conditions indicating coherent transport through the superlattice miniband. With increasing transverse magnetic fields, this peak is quenched and evidence of sequential LO-phonon scattering inside the superlattice is found. Using an extended transfer matrix method, the observed effects are quantitatively explained; differences to previous STM based measurements are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288232
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  • 2
    Electronic Resource
    Electronic Resource
    Intersubband absorption dynamics in coupled quantum wells (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2755-2757 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We apply an interband pump/intersubband probe technique to monitor the temporal evolution of the electron population in the first and second subband of an undoped GaAs/AlGaAs asymmetric double quantum well after interband optical excitation. The spacing between the two subbands is smaller than the longitudinal optical phonon energy. The time dependence of the intersubband absorption can be explained by a simple rate equation model. We extract an intersubband lifetime of T21=100 ps and a recombination time of τ=410 ps at an excitation density of nS=2×1011 cm−2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413728
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  • 3
    Electronic Resource
    Electronic Resource
    Antireflection coating for miniband transport and Fabry–Pérot resonances in GaAs/AlGaAs superlattices (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1486-1488 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated that standard concepts for optics like Fabry–Pérot resonances and antireflection coatings can be extended to ballistic electron transport in semiconductor superlattices. The transmission through a superlattice miniband is increased by a factor of 2.4 if two further barriers are added at both sides of the structure. The condition for Fabry–Pérot resonances for Bloch states in finite periodic potentials is derived and experimental evidence for their existence is obtained in transport experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1399315
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  • 4
    Electronic Resource
    Electronic Resource
    Self-aligned coupled cavity GaAs/AlGaAs midinfrared quantum-cascade laser (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1077-1079 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A monolithic GaAs/AlGaAs quantum-cascade laser with self-aligned focused ion beam-cut coupled cavities, emitting in the range of λ=9.4 μm is demonstrated. Separate pulsing of two optically coupled laser sections enables control of the lasing in single-mode and in multimode regimes. Side mode suppression ratios better than 25 dB are shown. Mode control over two single modes spaced by 3.6 cm−1 is presented. An optical output intensity modulation in a range of 20 dB is achieved. The laser exhibits a peak output power in the range of 180 mW at cryogenic temperatures. The observed mode spacing is in a good agreement with the calculation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289499
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous-wave operation of distributed feedback AlAs/GaAs superlattice quantum-cascade lasers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3328-3330 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on continuous-wave operation of first-order distributed feedback quantum-cascade lasers at λ=11.8 μm, based on interminiband transitions in a chirped AlAs/GaAs superlattice. Short devices operate in continuous-wave up to ∼30 K. The single-mode emission wavelength is continuously tunable with the temperature. A metallized surface-relief grating is used for feedback to achieve single-mode emission. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1328052
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  • 6
    Electronic Resource
    Electronic Resource
    Surface-emitting distributed feedback quantum-cascade lasers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2086-2088 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the realization of second-order distributed feedback quantum-cascade lasers at λ=9.35 μm, where the active region consists of GaAs, AlGaAs, and strained InGaAs grown on GaAs. A metal-stripe surface grating structure allows a high surface emission efficiency for the TM-polarized light. The emitted power via the surface is in the range of 100 mW and exceeds the emitted power from one facet. A double-lobed surface-emission far-field pattern is obtained for the lasing mode. The single-mode emission wavelength is continuously tunable by the heat sink temperature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1313807
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  • 7
    Electronic Resource
    Electronic Resource
    Terahertz quantum cascade structures: Intra- versus interwell transition (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1928-1930 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Terahertz quantum cascade structures (emission around 20 meV) based on intra- and interwell transitions have been compared in magnetotransport and intersubband-electroluminescence experiments. The interwell transition exhibits a Stark shift of up to 6 meV. We also observe a smaller energy shift of the intrawell transition which is attributed to the tunnel splitting, when the initial and final subbands mix with those of the injectors. The electric field induced narrowing of the emission line and our band structure calculations support this interpretation. The quantum efficiency of the electroluminescence is of similar magnitude for the two transitions, despite their large difference in the spatial subband overlap. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312864
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic-field-enhanced quantum-cascade emission (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 19-21 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed an enhancement of terahertz intersubband electroluminescence in a quantum cascade structure in the presence of a magnetic field applied normal to the epitaxial layers. At a field of B=7.2 T the emission efficiency doubles. This effect is attributed to the suppression of nonradiative Auger–intersubband transitions caused by Landau-quantization of the in-plane electron motion. The magnetic field dependence of the luminescence intensity shows strong oscillations. These magnetointersubband oscillations are caused by the modulation of the transition rate via resonant inter-Landau-level transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125642
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  • 9
    Electronic Resource
    Electronic Resource
    Narrow electron injector for ballistic electron spectroscopy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3639-3641 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A three-terminal hot electron transistor is used to measure the normal energy distribution of ballistic electrons generated by an electron injector utilizing an improved injector design. A triple barrier resonant tunneling diode with a rectangular transmission function acts as a narrow (1 meV) energy filter. An asymmetric energy distribution with its maximum on the high-energy side with a full width at half maximum of ΔEinj=10 meV is derived. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377852
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  • 10
    Electronic Resource
    Electronic Resource
    Quantum cascade lasers with monolithic air–semiconductor Bragg reflectors (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1241-1243 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrically pumped GaAs/AlGaAs quantum cascade lasers with monolithic one-dimensional photonic-band gap mirrors are presented. The mirrors consist of two, precisely defined grooves trenched across the laser ridge using a focused ion beam. A substantial improvement of the laser performance is achieved due to the increased reflectivity of these mirrors. A decrease of the threshold current by 40% at 150 K is observed. The maximum operation temperature increases from 155 K for an unmodified laser to 170 K for the laser with the modified mirrors, and an increase of the T0 parameter from 99 to 114 K is found. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289910
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