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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of an AlGaN/GaN two-dimensional electron gas structure (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 369-374 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An AlxGa1−xN/GaN two-dimensional electron gas structure with x=0.13 deposited by molecular beam epitaxy on a GaN layer grown by organometallic vapor phase epitaxy on a sapphire substrate was characterized. X-ray diffraction maps of asymmetric reciprocal lattice points confirmed that the thin AlGaN layer was coherently strained to the thick GaN layer. Methods for computing the aluminum mole fraction in the AlGaN layer by x-ray diffraction are discussed. Hall effect measurements gave a sheet electron concentration of 5.1×1012 cm−2 and a mobility of 1.9×104 cm2/V s at 10 K. Mobility spectrum analysis showed single-carrier transport and negligible parallel conduction at low temperatures. The sheet carrier concentrations determined from Shubnikov–de Haas magnetoresistance oscillations were in good agreement with the Hall data. The electron effective mass was determined to be 0.215±0.006 m0 based on the temperature dependence of the amplitude of Shubnikov–de Haas oscillations. The quantum lifetime was about one-fifth of the transport lifetime of 2.3×10−12 s. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371869
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple subband population in delta-doped AlAsSb/InGaAs heterostructures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1609-1611 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the Shubnikov–de Haas (SdH) effect in δ-doped AlAs0.56Sb0.44/In0.53Ga0.47As heterostructures and observed a population of the second subband. Using the persistent photoconductivity effect we increased the electron density from 26.73 to 28.20×1011 cm−2 in the first subband and 6.61 to 7.20×1011 cm−2 in the second. The onset of the second subband population occurs when the first subband is filled to a density of 11.56×1011 cm−2. From the nonparabolic band approximation we calculated the effective masses in both subbands before illumination. The effective mass for the second subband was evaluated using the temperature dependence of the SdH amplitude. Its value agrees well with the values obtained from the k⋅p approximation and infrared cyclotron resonance measurements. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363896
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  • 3
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity study in a high mobility AlGaN/GaN heterostructure (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6583-6588 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used the Shubnikov–de Haas and the Hall effects to investigate the effect of subband gap illumination on the transport properties of a very high mobility, μ=54 000 cm2/V s at T=1.2 K, Al0.09GaN0.91/GaN heterostructure. We have found that this illumination resulted in a photocurrent that was persistent at low temperatures. This photocurrent, which led to an increase in the carrier density, was used to study the dependence of the mobility and the quantum scattering time on the carrier density. Unlike in previous studies of persistent photoconductivity in GaN and AlGaN/GaN by other researchers, we have found that the mobility did not always increase with the carrier density as a result of illumination. For small duration of illumination, the mobility increased with the carrier density. However additional illumination resulted in a decrease of the mobility despite the increase in the carrier density. We believe that screening is responsible for the initial increase in the mobility, while ionization of defects in GaN, interface charges, and alloy disorder may be responsible for the eventual decrease in the mobility. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1322386
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  • 4
    Electronic Resource
    Electronic Resource
    Two-dimensional electron gas properties of AlGaN/GaN heterostructures grown on 6H–SiC and sapphire substrates (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 963-965 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality Al0.15Ga0.85N/GaN heterostructures have been fabricated on 6H–SiC and sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). A temperature independent mobility, indicative of the presence of a two-dimensional electron gas (2DEG), was observed in all samples below 80 K. The highest low temperature 2DEG mobility, 7500 cm2/V s, was measured in AlGaN/GaN grown on 6H–SiC; the sheet carrier density was 6×1012 cm−2. Strong, well resolved, Shubnikov–de Haas oscillations were observed in fields as low as 3 T and persisted to temperatures as high as 15 K. Hall effect measurements also revealed the presence of well-defined plateaus in the Hall resistance. The high quality 2DEG properties of the AlGaN/GaN heterostructures grown on 6H–SiC are attributed to the absence of significant parallel conduction paths in the material. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117096
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  • 5
    Electronic Resource
    Electronic Resource
    High mobility in n-type GaN substrates (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1873-1875 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High peak electron mobilities were observed in freestanding c-plane GaN layers. Two well-defined electrical layers, a low mobility degenerate interface layer, and a high mobility nondegenerate bulk layer, were present in these samples. The carrier concentrations and mobilities for the layers were extracted using two methods: (1) magnetic field dependent Hall effect analysis; and (2) a simple two layer Hall model with the assumption that one of the layers is degenerate. The electron Hall mobility of the bulk layer is found to peak at nearly 8000 cm2/V s at low temperature using the magnetic field dependent Hall effect analysis. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1348304
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