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  • 1
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    Contact regrowth technique for low-resistance nonalloyed contacts to the hot-electron transistor (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A novel contact regrowth technique for the formation of extremely low nonalloyed ohmic contacts is reported. The successful demonstration of this technique is reported on an InGaAs/InAlAs hot-electron transistor device. For the investigated InGaAs-based structure, the regrown contacting scheme reported includes an In(0.53)Ga(0.47)As layer, an InAs/GaAs strained-layer superlattice, and an InAs cap, all heavily doped n type with Si. A very low specific contact resistance of 1.8 x 10 to the -7th ohm sq cm to the base layer is obtained. The higher current densities achieved in the transistor characteristics are in close agreement with calculations, and a contact model is presented explaining the poor results of conventional nonalloyed contacts.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 53; 1738-174
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  • 2
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    Extremely low resistance nonalloyed ohmic contacts on GaAs using InAs/InGaAs and InAs/GaAs strained-layer superlattices (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Employing a structure consisting of n(+)-InAs/InGaAs and InAs/GaAs strained-layer superlattices (SLSs) grown by molecular beam epitaxy on GaAs films, nonalloyed contact resistances less than 8.5 x 10 to the -8th ohm sq cm have been obtained. Self-consistent simulations show that these extremely small nonalloyed contact resistances are due to the suppression of the depletion depth in the GaAs channel and tunneling through the SLS layer. Similar structures on InGaAs channels have led to nonalloyed specific contact resistances of about 1.5 x 10 to the -8th ohm sq cm. These results represent the smallest figures reported for these important material systems.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 53; 900
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  • 3
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    InGaAs/InAlAs hot-electron transistor (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Using InGaAs for the base and InAlAs for the emitter and collector barriers, the first hot-electron transistor in this material system is fabricated. It is shown that 1.6 percent of the injected hot electrons can be transported ballistically through a 0.3 micron thick In(0.53)Ga(0.47)As plus 800-A-thick InAlAs barrier layer at 77 K giving rise to an average mean free path of 920 A. An energy spread of 130 MeV was observed for the ballistic electrons injected at about 700 MeV above the thermal equilibrium conditions. The value of collector barrier heights measured are in reasonable agreement with those deduced independently from thermionic emission studies in InGaAs gate, InAlAs/InGaAs capacitor structures.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 48; 1799-180
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  • 4
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    Calculation of the electron wave function in a graded-channel double-heterojunction modulation-doped field-effect transistor (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Three double-heterojunction modulation-doped field-effect transistor structures with different channel composition are investigated theoretically. All of these transistors have an In(x)Ga(1-x)As channel sandwiched between two doped Al(0.3)Ga(0.7)As barriers with undoped spacer layers. In one of the structures, x varies from 0 from either heterojunction to 0.15 at the center of the channel quadratically; in the other two, constant values of x of 0 and 0.15 are used. The Poisson and Schroedinger equations are solved self-consistently for the electron wave function in all three cases. The results showed that the two-dimensional electron gas (2DEG) concentration in the channel of the quadratically graded structure is higher than the x = 0 one and slightly lower than the x = 0.15 one, and the mean distance of the 2DEG is closer to the center of the channel for this transistor than the other two. These two effects have important implications on the electron mobility in the channel.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters (ISSN 0003-6951); 55; 1223-122
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  • 5
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    Analysis of energy states in modulation doped multiquantum well heterostructures (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A precise and effective numerical procedure to model the band diagram of modulation doped multiquantum well heterostructures is presented. This method is based on a self-consistent iterative solution of the Schroedinger equation and the Poisson equation. It can be used rather easily in any arbitrary modulation-doped structure. In addition to confined energy subbands, the unconfined states can be calculated as well. Examples on realistic device structures are given to demonstrate capabilities of this procedure. The numerical results are in good agreement with experiments. With the aid of this method the transitions involving both the confined and unconfined conduction subbands in a modulation doped AlGaAs/GaAs superlattice, and in a strained layer InGaAs/GaAs superlattice are identified. These results represent the first observation of unconfined transitions in modulation doped multiquantum well structures.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Solid-State Electronics (ISSN 0038-1101); 33; 247-258
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  • 6
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    Cryogenic operation of pseudomorphic AlGaAs/InGaAs single-quantum-well MODFETs (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The 77 K operation of AlGaAs/InGaAs MODFETs has been investigated. The structures, grown by MBE, make use of a 200 A undoped In(0.15)Ga(0.85)As quantum well for electron confinement and an Si-doped Al(0.15)Ga(0.85)As top barrier. The MODFETs with 1 micron gate lengths exhibit extrinsic transconductances of 360 mS/mm and maximum currents of 310 mA/mm at 77 K. The use of a low Al mole fraction AlGaAs/InGaAs heterojunction makes it possible to avoid the persistent trapping effects encountered in AlGaAs/GaAs MODFETs without sacrificing device performance.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Electronics Letters (ISSN 0013-5194); 21; 937-939
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  • 7
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    Determination of carrier saturation velocity in high-performance In(y)Ga(1-y)As/Al(x)Ga(1-x)As modulation-doped field-effect transistors (with y between 0 and 0.2) (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The relation between the intrinsic transconductance per unit gate width and the carrier saturation velocity, v(sat), is used to determine v(sat) for several high-performance pseudomorphic MODFET's with different InAs mole fractions (y). Measurements of In(y)Ga(1-y)As/AlGaAs MODFET's grown by MBE were found to give accurate v(sat) values at 77 K. Devices with y between 0 and 0.20 were shown to have higher v(sat) than conventional GaAs/AlGaAs MODFET's. An optimum y value for peak v(sat), which may optimize overall device performance, is expected.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Electron Device Letters (ISSN 0741-3106); EDL-7; 288-290
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  • 8
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    High-frequency noise of In(y)Ga(1-y)As/Al(x)Ga(1-x)As MODFETs and comparison to GaAs/Al(x)Ga(1-x)As MODFETs (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Noise parameter measurements for recently developed 1 micron gate In(y)Ga(1-y)As/Al(0.15)Ga(0.85)As MODFETs have been performed at 8 GHz art room and cryogenic temperatures. Owing to the relatively small C(gs/sq rt) g(m) ratio in these devices compared to identical conventional GaAs/AlGaAs MODFETs, both room- and cryogenic temperature noise figures have been reduced. In addition, the light sensitivity and drift in noise figure at cryogenic temperatures observed in conventional GaAs/AlGaAs MODFETs have been substantially reduced.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Electronics Letters (ISSN 0013-5194); 22; 578-580
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