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  • 1
    Digitale Medien
    Digitale Medien
    Magnetic field-induced suppression of acoustic phonon emission in a superlattice (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 841-845 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We analyze theoretically the influence of magnetic field on the electron lifetime in the excited state of a specially designed superstructure allowing electron injection into the excited miniband. We show that the discrete electron energy spectrum arising in the magnetic field dramatically suppresses the acoustic phonon emission rate and gives rise to electron accumulation in the excited subband. This can be used for obtaining stimulated emission between minibands as well as between Landau levels. The latter is of particular interest since the energy of this radiation can be varied by magnetic field. We also obtain an oscillatory dependence of electron lifetime in the excited state on magnetic field which can be verified in a simple photoluminescence experiment. Finally, we extend our considerations to the case of quantum dots, capable of providing complete energy quantization in the absence of magnetic field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347319
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  • 2
    Digitale Medien
    Digitale Medien
    Current-controlled negative differential resistance in four-terminal heterostructure devices (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2452-2454 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate new effects of the current-controlled (S-shaped) negative differential resistance (NDR) in different circuit configurations of four-terminal modulation-doped AlGaAs/GaAs heterostructure devices, with the magnitude of the voltage drop varied by external electrodes. We observe two S-shaped instabilities having different physical origins. One effect arises due to an avalanche in the top AlGaAs layer underneath the reverse-biased gate region. Another phenomenon relies on the creation, during the avalanche, of nonequilibrium hot electrons at the conducting channel (quantum well). This dramatically enhances electron flow over the heterostructure barriers and gives rise to a strongly pronounced current-controlled NDR with a peak-to-valley ratio of ∼10.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101069
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  • 3
    Digitale Medien
    Digitale Medien
    Junction field-effect transistor single quantum well optical waveguide modulator employing the two-dimensional Moss–Burstein effect (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2177-2179 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A modulation-doped junction field-effect transistor incorporating an optical waveguide under the gate modulates light by the carrier band-filling effect (two-dimensional Moss–Burstein effect) in a single quantum well, achieving a 5:1 extinction ratio in a 250-μm-long waveguide for 4 V reverse gate-source bias Vgs swing and 0 V drain-source bias Vds. Similar performance is obtained over a 16 nm spectral range. A novel band-edge transparency effect is observed for Vds〉0 allowing an extinction ratio of 10:1, corresponding to a change in absorption of 92 cm−1 to be obtained through band-gap dilation by hot electrons at biases of Vds =8 V. Below-band-gap refractive index modulation of 1.6×10−3 is obtained for a Vgs swing of 2.4 V. The novel junction field-effect transistor optical modulator also functions as a photovoltaic or photoconductive optical detector, a transistor, and a light-emitting diode.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101157
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  • 4
    Digitale Medien
    Digitale Medien
    Quantum well tunnel triode (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 398-400 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate a novel three-terminal device, the tunnel triode, in which the current within the quantum well is a part of the tunnel current through the p+-n+ junction. A tunnel-diode-like negative differential resistance effect with peak-to-valley ratio as high as 20 was observed, the tunnel current being controlled by the gate voltage. We show that tunneling occurs not in the quantum well, but in the heavily doped n+-Al0.3Ga0.7As layer, and it is preceded by a real-space hot-electron transfer from the quantum well into this layer. Logic operation of a bistable switch was obtained in a circuit comprising a tunnel triode and a series resistance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99478
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  • 5
    Digitale Medien
    Digitale Medien
    Photovoltaic detection of infrared light in a GaAs/AlGaAs superlattice (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1320-1322 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the observation of photovoltaic infrared photodetection in an n-type GaAs/AlGaAs superlattice within the optical range 3.6–6.2 μm. A built-in graded AlGaAs barrier (∼0.2 eV) provides charge polarization in the sample by allowing the optically excited electrons in the second miniband of the superlattice to diffuse over this barrier. The optical polarization of the infrared signal is consistent with the selection rules applicable to the superlattice. The infrared photoresponse results from first-to-second miniband as well as shallow donor-to-second miniband photoexcitations within the superlattice. Donor-to-second miniband photoexcitation is dominant at low temperatures (〈25 K).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99147
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  • 6
    Digitale Medien
    Digitale Medien
    Novel high-speed transistor based on charge emission from a quantum well (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 904-906 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A novel unipolar transistor employing properties of electrons confined in a single quantum well is proposed. The gate modulation of a charge density in the quantum well results in an exponentially strong variation of the output thermionic emission current to the collector. The device combines the attractive features of both bipolar and field-effect transistors and provides a high speed (2–3 ps intrinsic delay time) with a large current drive (∼105 A/cm2) and high transconductances (1–10 S/mm).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99268
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  • 7
    Digitale Medien
    Digitale Medien
    Hybrid superconductor/semiconductor step junctions with three terminals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 8077-8079 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on experimental results with three-terminal superconductor/semiconductor hybrid junctions, which are based on the two-dimensional electron gas at the surface of p-type InAs. A short distance ((approximate)150 nm) between superconducting Nb contacts is obtained using a step geometry. The step geometry allows the realization of different heterostructure potential profiles along the two-dimensional channel. The critical current of the step junctions can be controlled by applying a voltage to highly doped (δ-doped) layers embedded in the heterostructure. With p-δ-doped layers, a p-n junction is introduced in the two-dimensional channel and an asymmetric change of the critical current with respect to the gate voltage or gate current is observed. With n-δ-doped layers, the change is symmetrical. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.367905
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  • 8
    Digitale Medien
    Digitale Medien
    Ohmic, superconducting, shallow AuGe/Nb contacts to GaAs (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3204-3210 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An emerging new class of superconductor-semiconductor devices requires Ohmic superconducting contacts which do not diffuse deeply into a semiconductor. We developed a contact to GaAs based on ∼150 A(ring) of AuGe covered with ∼2000 A(ring) of Nb annealed in reducing atmosphere at 390–420 °C for 1–5 s. The resulting contact has linear I-V characteristics at all temperatures down to 4.2 K, resistivity of ∼2×10−6 Ω cm2 (∼0.1 Ω mm), and superconducting transition temperature Tc (approximately-greater-than)8 K. Secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM) studies revealed very shallow penetration of the active dopant Ge into GaAs; the upper limit for the thickness of the doped layer with Ge concentration over 1017 cm−3 is estimated as 200–300 A(ring). Gold, a nonactive dopant (deep level) drops to below 1018 cm−3 within the same distance, with the possible tail extending further. Morphology and uniformity of a contact, as revealed in TEM and optical microscopy, is good, owing to the Nb overlayer which prevents AuGe from "balling up'' upon melting. These contacts can be used in low-temperature devices and conventional devices based on GaAs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337738
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  • 9
    Digitale Medien
    Digitale Medien
    Quantum well emission transistor with tunneling output current (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 425-429 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We propose a novel tunneling quantum well emission transistor (TQWET), in which the gate-induced modulation of the Fermi level in the quantum well leads to a strong variation of the tunneling current to the collector through the specially designed collector barrier. The device is calculated to possess a high transconductance and a large current drive. Low-temperature utilization of the transistor implies a high electron mobility in the quantum well (QW) and, therefore, low lateral resistance along the QW, a major current and speed limitation of the device. With this limitation taken into account, the TQWET shows the delay times ∼1.4 and 1.5 ps for temperatures 10 and 77 K, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343840
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  • 10
    Digitale Medien
    Digitale Medien
    Theory of the quantum well emission transistor (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 821-829 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a theoretical analysis of the physical processes and high-speed performance of the recently proposed quantum well emission transistor employing quantum properties of electrons in a single quantum well (QW). The physical mechanism of device operation is based on an exponentially strong variation of the thermionic emission from the QW to the collector induced by the charge density modulation in the QW by the gate voltage. The calculation is performed for the selected structure optimized for the highest device performance.The most essential part of calculation is related to the effect of collector and gate voltages on the ground-state energy in the QW. A variational approach is used to take into account the presence of electrons in the QW. The analysis presented shows a high potential of this device for high-speed, large current drive applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343072
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