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  • 2000-2004  (58)
  • 1975-1979  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Metalorganic chemical vapor deposition of GaN on Si(111): Stress control and application to field-effect transistors (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7846-7851 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two schemes of nucleation and growth of gallium nitride on Si(111) substrates are investigated and the structural and electrical properties of the resulting films are reported. Gallium nitride films grown using a 10–500 nm-thick AlN buffer layer deposited at high temperature (∼1050 °C) are found to be under 260–530 MPa of tensile stress and exhibit cracking, the origin of which is discussed. The threading dislocation density in these films increases with increasing AlN thickness, covering a range of 1.1 to 〉5.8×109 cm−2. Films grown using a thick, AlN-to-GaN graded buffer layer are found to be under compressive stress and are completely crack free. Heterojunction field effect transistors fabricated on such films result in well-defined saturation and pinch-off behavior with a saturated current of ∼525 mA/mm and a transconductance of ∼100 mS/mm in dc operation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1372160
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of scattering by strain fields surrounding edge dislocations on electron transport in two-dimensional electron gases (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 64-66 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a theory of deformation potential carrier scattering of two-dimensional electron gases from the strain fields surrounding edge dislocations. The scattering rate is evaluated in closed form without any fitting parameters. The result is directed towards understanding mobility limiting scattering mechanisms for two-dimensional electron gases at AlGaN/GaN heterointerfaces. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429758
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  • 3
    Electronic Resource
    Electronic Resource
    Indium-surfactant-assisted growth of high-mobility AlN/GaN multilayer structures by metalorganic chemical vapor deposition (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3449-3451 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlN/GaN single and multilayer structures with various AlN and GaN layer thicknesses were grown by metalorganic chemical vapor deposition. Step flow growth of AlN was achieved using trimethylindium as a surfactant. Defect formation in the AlN layer could be largely prevented for AlN layers thinner than 2.9 nm. In the multiquantum-well samples, which consisted of five (AlN/GaN) periods, a two-dimensional electron gas (2DEG) was formed at the interface between the GaN base layer and the first AlN barrier layer. When the thickness of the AlN barrier layer in the multiquantum well was increased from 0.9 to 2.6 nm at a constant GaN well thickness of 5 nm, the sheet carrier density of the 2 DEG increased from 5×1012 to 2.1×1013 cm−2 and the electron mobility measured at 77 K decreased from 11780 to 3140 cm2/V s. The effect of the GaN well thickness was also investigated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420573
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  • 4
    Electronic Resource
    Electronic Resource
    Dislocation reduction in GaN films through selective island growth of InGaN (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2665-2667 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dislocation reduction in GaN films grown on sapphire and silicon substrates was achieved by inserting thin InGaN layers grown in a selective island growth mode after partial passivation of the GaN surface with a submonolayer of silicon nitride. We show that this technique is most effective at reducing the pure edge dislocation density when it is high (i.e., 〉1010 cm−2) and less when the density is in the 108–109 cm−2 range. Thus, the structural quality of typically highly dislocated GaN on silicon films could be significantly improved, visible in a reduction of the (0002) full width at half maximum (FWHM) from 1300 arcsec for ordinary GaN on silicon to 800 arcsec for GaN films with silicon nitride/InGaN interlayers. In the case of GaN layers grown on sapphire (dislocation density ∼109 cm−2), the method resulted mainly in a reduction of the FWHM of the (101¯2) and (202¯1) diffraction peaks. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319528
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  • 5
    Electronic Resource
    Electronic Resource
    Two-dimensional electron-gas AlN/GaN heterostructures with extremely thin AlN barriers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3998-4000 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-assisted molecular-beam epitaxy is used to grow a set of two-dimensional electron-gas AlN/GaN structures with AlN barrier thicknesses varied between 24 and 50 Å. The density of the two-dimensional electron gas formed at the GaN/AlN interface increases from 1.51×1013 cm−2 for the AlN barrier width of 24 Å to 3.65×1013 cm−2 for the AlN barrier width of 49 Å. The increase in the electron sheet density is accompanied by a decrease in electron mobility related to tensile strain relaxation and enhanced interface roughness scattering. It is shown that room-temperature sheet resistances below 200 Ω/(square, open) can be achieved in AlN/GaN high electron mobility transistor structures with 35–45 Å AlN barriers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1332408
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  • 6
    Electronic Resource
    Electronic Resource
    Mg doping of GaN layers grown by plasma-assisted molecular-beam epitaxy (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 718-720 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN:Mg layers grown by plasma-assisted molecular-beam epitaxy at 650 °C are investigated. Secondary-ion-mass-spectroscopy measurements reveal uniform Mg doping profiles with very sharp boundaries. The amount of incorporated Mg atoms changes approximately linearly with incident Mg flux. Hall measurements on p-type GaN:Mg layers show that about 1%–2% of all Mg atoms are ionized at room temperature. The hole mobility depends strongly on the hole concentration, varying from μp=24 cm2/V s for p=1.8×1017 cm−3 to μp=7.5 cm2/V s for p=1.4×1018 cm−3. GaN p–n diodes with molecular-beam-epitaxy-grown p regions are analyzed using current–voltage measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125872
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  • 7
    Electronic Resource
    Electronic Resource
    Reactive removal of misfit dislocations from InGaAs on GaAs by lateral oxidation (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 845-847 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Layers of hypercritical thickness InGaAs/AlAs/GaAs have been shown to strain relax when the underlying AlAs layer is laterally oxidized. InxGa1−xAs layers of composition 0.2≤x≤0.4 have been investigated at thicknesses in the range 5–20 times the Matthews–Blakeslee critical thickness hc. The amount of strain relieved does not depend on the InGaAs-layer thickness, the initial strain state, or the composition of the material, but it does strongly depend on the oxidation temperature. The structure of the strain-relaxed InGaAs layer has been investigated using plan-view transmission electron microscopy. It is shown that the misfit dislocation density in In0.3Ga0.7As grown to 15 times the critical thickness (660 Å) has been reduced by two orders of magnitude after lateral oxidation. It is proposed that this is due to interfacial oxidation, which consumes the misfit dislocation cores. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1306918
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  • 8
    Electronic Resource
    Electronic Resource
    Polarization effects, surface states, and the source of electrons in AlGaN/GaN heterostructure field effect transistors (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 250-252 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The origin of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructure field effect transistors is examined theoretically and experimentally. Based on an analysis of the electrostatics, surface states are identified as an important source of electrons. The role of the polarization-induced dipole is also clarified. Experimental Hall data for nominally undoped Al0.34Ga0.66N/GaN structures indicate that ∼1.65 eV surface donors are the actual source of the electrons in the 2DEG, which forms only when the barrier thickness exceeds 35 Å. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126940
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of growth termination conditions on the performance of AlGaN/GaN high electron mobility transistors (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3088-3090 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of the growth conditions of the top 2.5 nm thick AlGaN cap layer and wafer cool down conditions on AlGaN/GaN high electron mobility transistor performance was investigated. The AlGaN/GaN heterostructures were deposited on sapphire by metalorganic chemical vapor deposition and consisted of a 3 μm thick semi-insulating GaN layer and an 18 nm thick Al0.33Ga0.67N layer, the top 2.5 nm of which was deposited under various conditions. The power performance of the devices severely degraded for all samples where the Al content of the top 2.5 nm of AlGaN was increased and/or the ammonia flow during growth of the top layer was decreased. A modest improvement in the output power density was observed when the growth conditions of the cap layer were identical of those of the rest of the AlGaN layer, but when the wafer was cooled down in pure nitrogen. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1372620
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  • 10
    Electronic Resource
    Electronic Resource
    High voltage operation (〉80 V) of GaN bipolar junction transistors with low leakage (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2457-2459 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated the high voltage operation of n-p-n GaN bipolar junction transistors using regrown emitters. Devices were grown by metalorganic chemical vapor deposition on sapphire substrates. The n-type emitter was grown selectively on a base-collector p-n junction diode using a dielectric mask. A thin base (1000 Å) was used to increase the current gain over our previous result with a regrown emitter [J. B. Limb, L. McCarthy, P. Kozodoy, H. Xing, J. Ibbetson, Y. Smorchkova, S. P. DenBaars, and U. K. Mishra, Electron. Lett. 35, 19 (1999)]. The base contacts were better than expected despite the use of a thin base. Common emitter operation showing a voltage operation of over 80 V with negligible leakage has been demonstrated. Room temperature current gain was ∼3 corresponding to a current transfer ratio of ∼0.75. This results in a calculated minority carrier lifetime of about 80 pS in the base. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126375
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