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  • 1
    Electronic Resource
    Electronic Resource
    Transport and optical properties of AlGaAs/GaAs and pseudomorphic AlGaAs/InGaAs/GaAs heterostructures subjected to CH4/H2 reactive ion etching (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6242-6246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the effect of methane/hydrogen (CH4/H2) reactive ion etching (RIE) and a subsequent annealing process on AlGaAs/GaAs and pseudomorphic AlGaAs/InGaAs/GaAs heterostructures. We use low temperature Hall, Shubnikov–de Haas, and photoluminescence measurements. We observe that the electron density and mobility of the two-dimensional electron gas in the heterostructure is strongly reduced by the RIE process. After annealing the electron density fully recovers for both types of structures, whereas the electron mobility responds differently. While for the pseudomorphic AlGaAs/InGaAs/GaAs heterostructures thermal annealing restores the electron mobility completely, for the AlGaAs/GaAs heterostructures the electron mobility recovers only to 60% of the original value. This indicates that in the AlGaAs/GaAs heterostructures the structural damage induced by reactive ion etching is not fully removed by thermal annealing. This is confirmed by photoluminescence measurements at low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355166
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  • 2
    Electronic Resource
    Electronic Resource
    Optical investigation of the two-dimensional hole energy spectrum in GaAs/AlxGa1−xAs heterojunctions (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7775-7779 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of optical studies on the energy spectrum of a two-dimensional hole gas (2DHG) in a GaAs/AlxGa1−xAs structure. The photoluminescence (PL) line shape in the 2DHG is investigated as a function of temperature by heating the holes by a current flow through the 2D hole channel. The line shape of the PL from the 2DHG as a function of temperature is calculated by taking into account the real band structure and the hole–hole final-state interaction. By comparing experiment and theory, it is found that the special features of the band structure predicted theoretically explain the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353982
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  • 3
    Electronic Resource
    Electronic Resource
    Electric field induced parallel conduction in GaAs/AlGaAs heterostructures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 302-306 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new mechanism to understand time-dependent features in the conduction of a two-dimensional electron gas (2 DEG) in high electric fields is proposed and discussed. The mechanism is based on the idea that not only the properties of the GaAs/AlGaAs heterostructure have to be included, but also the properties of the transition from the ohmic contact to the heterostructure. We show that the ohmic contact to the heterostructure is fundamentally different from the contact to a bulk semiconductor. In low electric fields electrons cannot move from the contact into the AlGaAs since the conduction band normally lies above the Fermi level. However, when high enough electric fields are applied, the barrier between the contact and AlGaAs is pulled down, allowing conduction in both the AlGaAs and the 2 DEG. We propose a model, in which time-dependent phenomena in the conduction of the 2 DEG can be associated with trapping and detrapping of charge carriers in the AlGaAs. Time-resolved experiments are shown which confirm this hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347713
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  • 4
    Electronic Resource
    Electronic Resource
    Observation of current filaments in GaAs/AlxGa1−xAs heterostructures using a time-resolved imaging technique (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3330-3335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We developed a time-resolved optical beam induced current (TROBIC) technique, and performed time-resolved current imaging experiments on GaAs/AlxGa1−xAs heterostructures under high electric field conditions. These experiments are the first time-resolved imaging experiments of current patterns in a two-dimensional semiconductor structure. We attribute the current patterns observed in the TROBIC images to the formation of current filaments in the AlxGa1−xAs layer, parallel to the two-dimensional electron gas (2DEG). We show that even in samples where the two-dimensional electron gas and the contacts to the 2DEG are perfectly ohmic and homogeneous, current filaments can still develop in high electric fields. These temporal and spatial instabilities in the AlxGa1−xAs layer strongly affect the high-field transport properties of the heterostructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350954
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  • 5
    Electronic Resource
    Electronic Resource
    Origin of current instabilities in GaAs/AlxGa1−xAs heterostructures: Avalanche ionization in the AlxGa1−xAs layer (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2381-2385 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulsed current-voltage measurements on modulation-doped GaAs/AlxGa1−xAs heterostructures are presented at electric fields up to 2 kV/cm. At fields between 0.5 and 2.0 kV/cm we observe up to three well-defined avalanche type current jumps as a function of time. These current jumps show hysteresis effects as a function of the electric field. At even higher electric fields the current becomes irregular and we observe chaotic behavior. To explain the current instabilities we assume that at high electric fields electrons are injected into the AlxGa1−xAs layer parallel to the two-dimensional electron gas. The injected electrons subsequently cause avalanche ionization of occupied DX centers in the AlxGa1−xAs layer. Due to this process, a current filament is created with an exceptionally high mobility which is about 2×104 cm2/V s at 10 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353091
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  • 6
    Electronic Resource
    Electronic Resource
    Electrorefraction in strained InGaAs/InP chopped quantum wells: Significance of the interface layers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2331-2335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a model for electrorefraction based on the quantum confined Stark effect (QCSE) in strained InGaAs/InP chopped quantum wells (CQWs) consisting of three 27 Å InGaAs wells separated by 15 Å InP barriers. The model fully takes into account the influence of the thin interface layers around each well. We experimentally verify the model on a InGaAs/InP CQW which combines a large 60 meV QCSE redshift at 11.7 V bias with waveguide transparency at 1.55 μm, which is two times larger than in a InGaAsP quaternary well. The calculated electroabsorption spectra of the CQWs are in good agreement with experiment. We finally applied the Kramers–Kronig transformations for calculating the switching voltage in a Mach–Zehnder switch employing CQWs in the phase shifting section. The model was found to be in good agreement with experiment for both polarizations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372183
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  • 7
    Electronic Resource
    Electronic Resource
    Attenuation of picosecond electrical pulses by two-dimensional electron gases integrated in coplanar striplines (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3053-3057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the attenuation of picosecond electrical pulses by two-dimensional electron gases that are monolithically integrated in coplanar transmission lines. By integrating the two-dimensional electron gas structure into the transmission line, we avoid impedance mismatches that give rise to spurious reflection. The attenuated transients are simulated by an equivalent circuit transmission line model, where the conductivity of the two-dimensional electron gas underneath the transmission line is taken into account. The measured pulses are fitted with a specific conductivity of the layers corrected with a mode overlap factor, which describes the overlap of the electrical field lines with the two-dimensional layer. We obtain an overlap factor of 0.8–1.1. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361246
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrafast carrier dynamics at a metal-semiconductor interface (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6831-6838 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ultrafast carrier dynamics in the high electric field at an Au-GaAs interface has been studied experimentally as well as theoretically. The photoluminescence decay time is related directly to the carrier sweepout from the GaAs depletion region, i.e., to the time needed for photoexcited electrons and holes to leave this region. This decay time has been found to increase drastically with laser input power, ranging from a few picoseconds at low excitation to values of 10–20 ps at high excitation. These results indicate a significant retardation of the sweepout, which cannot be explained by intervalley scattering and space-charge effects. From our Monte Carlo calculations it has been found that the applied electric field collapses totally almost instantaneously after laser excitation due to the enormous excess of photoexcited charges. The sweepout only recovers after some time needed to recharge the device. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363749
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  • 9
    Electronic Resource
    Electronic Resource
    Optimization of barrier thickness for efficient carrier capture in graded-index and separate-confinement multiple quantum well lasers (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2767-2769 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results from numerical calculations on the carrier capture efficiency in separate- confinement and graded-index separate-confinement multiple quantum well (MQW) lasers. We find that the capture time oscillates as a function of the well width as well as the barrier width between the wells, due to a changing overlap of the barrier wave functions with the bound states in the wells. We show that one order of magnitude improvement in the carrier capture efficiency can be accomplished by properly choosing the dimensions of the layers in the active region of the MQW laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104780
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  • 10
    Electronic Resource
    Electronic Resource
    Electro-optic voltage profiling of modulation-doped GaAs/AlGaAs heterostructures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1763-1765 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electro-optic effect of GaAs is applied to profile the voltage distribution of the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. In our setup we reached a voltage sensitivity of 2 mV. We used this technique to characterize the local resistivity of the 2DEG. The results are consistent with those obtained from scanning electron microscopy voltage contrast measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101284
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