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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of deep-level defects in GaAs irradiated by 1 MeV electrons (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 640-647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep level transient spectroscopy has been employed to determine the defect energy levels, capture cross sections, and trap densities in Si-doped vapor phase epitaxy GaAs both before and after irradiation by 1 MeV electrons at room temperature for electron fluence ranging from 1.1×1014 to 5.0×1015 e cm−2. The results indicate that the irradiated samples have an electron trap at Ec-0.334 eV(EL6) in addition to the two electron traps at Ec-0.815 eV(EL2) and Ec-0.420 eV(EL3) which are present in the nonirradiated sample. The density of the EL6 trap increases monotonically with irradiation fluence from 6.7×1013 to 24.4×1013 cm−3 as electron fluence is increased from 1.1×1014 to 3.1×1014 e cm−2. In contrast, both the EL2 and EL3 trap densities were found to be only moderately affected by electron irradiation with trap densities slightly greater than the nonirradiated sample. These results, along with the fact that the EL6 trap was not observed in the nonirradiated sample, strongly suggest that this trap is created by the electron irradiation. In addition to creating the EL6 trap, electron irradiation results in a nonexponential transient for the EL2 deep level at Ec-0.815 eV which can be resolved into the sum of two exponential transients arising from two closely spaced deep levels at Ec-0.815 eV and Ec-0.843 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353375
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  • 2
    Electronic Resource
    Electronic Resource
    Interface-state density analysis of thermally and electron-beam-annealed GaAs surfaces (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7146-7152 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Schottky diodes were formed on n-GaAs surfaces that had undergone furnace and scanned electron beam (SEB) heat treatments that are similar to those typically used for Ohmic contact formation. The diode parameters of heat-treated samples were inferior to those that were not heat treated. The interface-state density Dit, determined from Tseng and Wu's interfacial layer model, was found to exhibit a strong correlation with the heat treatments, with furnace-annealed samples exhibiting progressively larger Dit values than SEB annealed samples. The presence of a spin-on glass capping layer during heat treatment resulted in reduced Dit values. Photochemical passivation of the GaAs surface before Schottky metal deposition resulted in a reduction in the interface-state density. Controlled etching of a heat-treated GaAs surface revealed that the surface damage caused by heat treatments extends to about 500 nm. Elevated thermal aging studies of Schottky contacts show a monotonic increase in Dit with aging time, irrespective of surface preparation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347605
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  • 3
    Electronic Resource
    Electronic Resource
    Scattering mechanisms limiting two-dimensional electron gas mobility in Al0.25Ga0.75N/GaN modulation-doped field-effect transistors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3900-3904 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to characterize the electron transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN modulation-doped field-effect transistors, channel magnetoresistance has been measured in the magnetic field range of 0–12 T, the temperature range of 25–300 K, and gate bias range of +0.5 to −2.0 V. By assuming that the 2DEG provides the dominant contribution to the total conductivity, a one-carrier fitting procedure has been applied to extract the electron mobility and carrier sheet density at each particular value of temperature and gate bias. Consequently, the electron mobility versus 2DEG sheet density has been obtained for each measurement temperature. Theoretical analysis of these results suggests that for 2DEG densities below 7×1012 cm−2, the electron mobility in these devices is limited by interface charge, whereas for densities above this level, electron mobility is dominated by scattering associated with the AlGaN/GaN interface roughness. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372432
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of magnetic field dependent Hall data in narrow bandgap Hg1−xCdxTe grown by molecular beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3881-3892 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The analysis of magnetic field dependent Hall data is presented for three representative Hg1−xCdxTe layers grown by Molecular Beam Epitaxy with x in the range 0.193 to 0.244. These samples exhibit "anomalous'' Hall characteristics which are analyzed using a hybrid approach consisting of mobility spectrum (MS) analysis followed by a multi-carrier fitting (MCF) procedure. This hybrid approach is able to readily separate contributions to the total conductivity arising from extrinsic carriers, thermally activated intrinsic electrons, and two-dimensional electron layers. The extracted transport parameters for thermally activated intrinsic electrons are shown to be in excellent agreement with established physical models for narrow bandgap HgCdTe. The two-dimensional electron layers are found to be only weekly temperature dependent with an electron mobility in the range of 2 to 4×104 cm2/V s and a sheet density in the range of 1011 to 1012 cm−2. Of particular interest, is the fact that the "anomalous'' Hall characteristics exhibited by all three samples are shown not to be indicative of poor-quality material. This anomalous behavior is found to be due to comparable contributions to the total conductivity from either bulk majority carrier holes and intrinsic minority electrons, or bulk majority carriers and a two-dimensional electron population. The practical aspects of implementing the MS+MCF procedure are discussed, with particular emphasis on the range of magnetic fields required for unambiguous and accurate parameter extraction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363344
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of neutron and electron irradiation on the EL2 defect in GaAs (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2985-2988 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The deep level transient spectroscopy technique has been used to study the EL2 defect in n-type semiconducting GaAs subjected to 1 MeV fast neutrons at room temperature. After neutron irradiation, the EL3 defect which is usually detected between 180 and 210 K disapperared and the EL2 defect measured between 280 and 320 K was found to remain single exponential (Ec−0.820 eV) despite the creation of a broad U band measured between 100 and 270 K. From this result, together with our earlier reports on the double exponential capacitance transient of the EL2 defect after 1 MeV electron irradiation [Lai, Nener, Faraone, Nassibian, and Hotchkis, J. Appl. Phys. 73, 640 (1993)] and the behavior of the electron irradiated EL2 defect upon isochronal annealing [Lai and Nener, J. Appl. Phys. 75, 2354 (1994)], we observe a difference in the behavior of the EL2 defect after neutron and electron irradiation. The results of the present study indicate that the EL2-B level reported in an earlier work is not due to any interaction of the stable EL2 (or EL2-A) level with either the U-band or EL6 defect. The EL2 defect is likely to be a complex defect which can manifest itself as a number of different defect levels depending on the particular details of the irradiation used. The U band is likely to be a cluster defect caused by the large number of atoms displaced from lattice sites by the fast neutrons, and is not likely to be due to any interaction mechanism between the EL2 and EL6 defects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358715
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  • 6
    Electronic Resource
    Electronic Resource
    Scanning laser microscopy of reactive ion etching induced n-type conversion in vacancy-doped p-type HgCdTe (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3443-3445 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-beam-induced-current measurements have been used to characterize the extent of reactive ion etching (RIE) induced type conversion in vacancy-doped p-type Hg0.69Cd0.31Te. The technique allows the spatial extent of RIE induced type conversion to be determined and the donor level concentration profile within the n-type converted region to be estimated. For the RIE processing conditions used (410 mT, CH4/H2, 0.4 W/cm2) and an etch depth of 0.2 μm, n-type conversion extending ∼1.5 μm into the semiconductor was observed. The simple and powerful approach developed in this work is of general application to the study of semiconductor junctions, and can be applied to a range of processing techniques used in the formation of p-n junctions in HgCdTe (e.g., epitaxially grown heterojunctions, ion implantation, ion milling and Hg in-diffusion). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119159
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic field dependent Hall data analysis of electron transport in modulation-doped AlGaN/GaN heterostructures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2996-3002 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental magnetic field dependent Hall and resistivity data is presented for two modulation-doped AlGaN/GaN heterostructures in the temperature range from 6 to 300 K and for a magnetic field up to 12 T. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface and within the underlying GaN layer are readily separated and characterized using quantitative mobility spectrum analysis. The observed transport parameters of the 2DEG are explained using the classical band theory for a degenerate electron gas. Analysis of the temperature dependencies of mobility and electron concentration in the GaN layer and 2DEG indicates that electron transport in the GaN layer is dominated by carriers in the conduction band for the case of low-doping (〈1017 cm−3), and by conduction via an impurity band for highly doped material (〉1018 cm−3). The simultaneous analysis of the multilayer AlGaN/GaN structure applied in this work renders the results applicable directly to modulation-doped field-effect transistors based on similar structures. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366137
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  • 8
    Electronic Resource
    Electronic Resource
    Mercury annealing of reactive ion etching induced p- to n-type conversion in extrinsically doped p-type HgCdTe (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5555-5557 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mercury annealing of reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type epitaxial layers of HgCdTe (x=0.31) has been used to reconvert n-type regions created during RIE processing. For the RIE processing conditions used (400 mT, CH4/H2, 90 W), p- to n-type conversion was observed using laser beam induced current (LBIC) measurements. After a sealed tube mercury anneal at 200 °C for 17 h, LBIC measurements clearly indicated that no n-type converted region remained. Subsequent Hall measurements confirmed that the material consisted of a uniform p-type layer, with electrical properties equivalent to that of the initial as-grown wafer (NA−ND=2×1016 cm−3, μ=350 cm2 V−1 s−1). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367389
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of doping density in HgCdTe p-n junctions using scanning laser microscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 52-54 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantitative assessment of p- to n- type conversion due to reactive ion etching (RIE) of p-type Hg0.71Cd0.29Te is presented using laser-beam-induced-current (LBIC) measurements. For the RIE processing conditions used (390 mT, CH4/H2, 0.4 W/cm2), n-type conversion was observed in extrinsic arsenic-doped p-type Hg0.71Cd0.29Te which had previously undergone a Hg anneal to eliminate Hg vacancies. Effective doping density of the n-type converted region is determined by fitting a theoretically determined LBIC signature to the measured LBIC signal over a temperature range 80–300 K. Effective n-type doping density is the only fitting parameter used in the simulation, which was carried out using a commercial semiconductor device modeling package (SEMICAD™ DEVICE). This noncontact experimental technique promises to be a useful tool in the characterization of p-n junction diodes in HgCdTe, and for studying the precise nature of p to n conversion in p-type HgCdTe. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120642
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  • 10
    Electronic Resource
    Electronic Resource
    Numerical simulation of temperature distributions during electron beam annealing of multilayer semiconductor structures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 7050-7058 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A finite element method has been used to study temperature profiles in multilayer semiconductor structures. Of particular interest is the modeling of a continuous wave energy beam similar to those typically used for electron, laser, or ion beam annealing of semiconductor layers. The intensity of the heat source has been modeled in the form of a Gaussian disk on the surface of the structure. Using experimental data and appropriate curve fitting, mathematical expressions are derived that model both thermal conductivity and specific heat as a function of both temperature and sample composition. The resulting expressions give interpolation errors of less than 1% when compared with tabulated experimental values. The simulated temperature distributions are obtained by numerically solving the Helmholtz equation in cylindrical coordinates. Results are presented of simulations involving multilayer structures consisting of metal, insulating, and semiconducting films typically used in both silicon and gallium arsenide technology. The calculated temperature distributions point to possible large variations in substrate temperature as a consequence of lack of thorough control over the beam parameters. More specifically, the diameter of the energy beam is found to strongly affect the resultant peak temperature. The presence of either metal and/or dielectric layers on the surface of the semiconducting substrates is found to have a profound effect on the simulated temperature distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345053
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