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  • 1
    Digitale Medien
    Digitale Medien
    Photon-assisted tunneling in a resonant tunneling diode: Stimulated emission and absorption in the THz range (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2816-2818 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dc I–V characteristic of a triple-barrier resonant tunneling diode (RTD) integrated in a bowtie antenna and driven by THz radiation displays up to five additional resonant tunneling channels. These channels appear as additional peaks in the I–V characteristic whose voltage positions vary linearly with frequency in the investigated range between ν=1.0 and 3.4 THz. We attribute these peaks to photon-assisted tunneling processes corresponding to absorption and stimulated emission of up to three photons. The experiments suggest that such a device can be utilized to detect and generate THz radiation. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.114794
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  • 2
    Digitale Medien
    Digitale Medien
    Plasmons in a superlattice in a parabolic quantum well (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3165-3167 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Well-defined plasma oscillations are observed in a superlattice miniband even though the Fermi energy lies in the minigap. Despite the complex band structure, the resonance shows a remarkable insensitivity to changes in the number of electrons in the parabolic well in which the superlattice is placed, a feature of the generalized Kohn theorem that is expected only in the limit that the Fermi energy is near the bottom of the lowest miniband. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115150
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  • 3
    Digitale Medien
    Digitale Medien
    Temperature of quasi-two-dimensional electron gases under steady-state terahertz drive (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 829-831 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We use photoluminescence to study the time-average energy distribution of electrons in the presence of strong steady-state drive at terahertz (THz) frequencies, in a modulation-doped 125 A(ring) AlGaAs/GaAs square well that is held at low lattice temperature TL. We find that the energy distribution can be characterized by an effective electron temperature, Te((approximately-greater-than)TL), that agrees well with values estimated from the THz-illuminated, dc conductivity. This agreement indicates that under strong THz drive, LO phonon scattering dominates both energy and momentum relaxation; that the carrier distribution maintains a heated, thermal form; and that phonon drift effects are negligible. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116547
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  • 4
    Digitale Medien
    Digitale Medien
    Tunneling induced transparency: Fano interference in intersubband transitions (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3455-3457 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the observation of tunneling induced transparency in asymmetric double quantum well structures. Resonant tunneling through a thin barrier is used to coherently couple the two upper states in a three level system of electronic subbands in a GaAs/AlGaAs structure. This creates Fano-type interferences for the collective intersubband excitations in the absorption from the ground state, analogous to electromagnetically induced transparency (EIT) in atomic systems. We observe a 50% reduction in absorption between the subband resonances which can be explained by taking into account the coherent coupling of the upper states. We analyze the bias dependent absorption spectra and determine the relevant lifetime broadening and dephasing rates for the transitions. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119199
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  • 5
    Digitale Medien
    Digitale Medien
    Cryogenic scanning probe characterization of semiconductor nanostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 671-673 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate the use of a scanned probe microscope (SPM) at 4 Kelvin to study electron transport through a ballistic point contact in the two-dimensional electron gas inside a GaAs/AlGaAs heterostructure. The electron gas density profile is locally perturbed by the charged SPM tip providing information about the electron flow through the point contact. As the tip is scanned, one obtains a spatial image of the ballistic electron flux as well as the topographic profile of the structure. Calculations indicate the spatial resolution is comparable to the electron gas depth. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117801
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  • 6
    Digitale Medien
    Digitale Medien
    Interface roughness and alloy-disorder scattering contributions to intersubband transition linewidths (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2554-2556 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report measurements of intersubband absorption in single semiconductor quantum wells of different well widths and alloy compositions. The well width dependence of the intersubband absorption linewidth is consistent with broadening dominated by interface roughness. The linewidth, however, is found to be relatively unaffected by alloy composition in the quantum well, making alloying an effective tool in the design of quantum well optical devices relying on intersubband transitions. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117737
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  • 7
    Digitale Medien
    Digitale Medien
    Imaging and magnetometry of switching in nanometer-scale iron particles (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3269-3271 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The reversal mechanisms in arrays of nanometer-scale (〈40 nm diameter) iron particles are studied by low-temperature Hall magnetometry and room-temperature magnetic force microscopy. Rotation of the net array magnetization at low temperatures (20 K) occurs by both reversible and irreversible modes, the latter revealed by Barkhausen jumps. Spatially resolved measurements at room temperature show the particles to be single domain with remanence and coercivity indicating they are not superparamagnetic. Individual particles are observed to switch irreversibly over a small field range (〈10 Oe) between preferred magnetic directions parallel to the growth direction of the particles. Scaling of the arrays offers the possibility of magnetic storage at the 45 Gbit/in.2 level, nearly 50 times greater than current technology. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118032
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  • 8
    Digitale Medien
    Digitale Medien
    Strain-sensing cryogenic field-effect transistor for integrated strain detection in GaAs/AlGaAs microelectromechanical systems (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3763-3765 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have fabricated a strain-sensing cryogenic field-effect transistor (FET) from a GaAs/AlGaAs heterostructure containing a near-surface two-dimensional electron gas. The FET has transconductance 100 μS and a small signal drain-source resistance 10 MΩ. The charge noise has a flat spectrum at high frequencies with magnitude 0.2e/(square root of)Hz and 1/f noise corner less than 300 Hz. The piezoelectric effect couples stress in the substrate to the electron density in the FET channel giving an electrical response to applied strain. Strain sensitivity was measured to be 2×10−9/(square root of)Hz, limited by FET noise. Integrated strain-sensing FETs offer advantages for detecting small forces in GaAs/AlGaAs microelectromechanical systems. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115999
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  • 9
    Digitale Medien
    Digitale Medien
    Interface between low-temperature grown GaAs and undoped GaAs as a conduction barrier for back gates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3459-3461 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a back gated 2DEG (two-dimensional electron gas) structure using low-temperature grown (LTG) GaAs as a barrier layer between the back gate and the undoped GaAs channel. The sheet concentration of the 2DEG can be linearly varied from full depletion up to 3×1011 cm−2 at 12 K. When this charge modulation is modeled by a simple parallel plate capacitor, we find that the distance between the plates is approximately equal to the channel thickness rather than the actual spacing between the 2DEG and the back gate (which is the channel thickness plus the LTG GaAs thickness). We explain this behavior by observing that the leakage path is limited by the triangular barrier to conduction formed at the interface between the LTG GaAs defect band and the undoped GaAs channel conduction band. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.113387
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  • 10
    Digitale Medien
    Digitale Medien
    Logarithmically graded quantum well far-infrared modulator (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 348-350 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have designed and fabricated a remotely doped "logarithmic'' potential well intended to have a tunable, narrow band absorption at far-infrared frequencies. A surface gate, epitaxially grown backgate, and contact to the electron gas in the quantum well allow independent control of the absorption frequency and the integrated absorption strength. The resonance frequency is dominated by the well curvature at the potential minimum and can be Stark shifted from ω/2πc=35 cm−1 to a frequency of 125 cm−1 by moving the electron gas through the asymmetric well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111144
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