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  • 1
    Electronic Resource
    Electronic Resource
    Photon assisted reduction of interface charge between CdTe substrates and metalorganic chemical vapor deposition CdTe epilayers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 995-997 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel photothermal in situ surface pretreatment that reduces the interface charge between p-type CdTe substrates and CdTe epilayers grown by metalorganic chemical vapor deposition is reported. Prior to the actual growth of the epilayers, the substrates are held at 450 °C in hydrogen atmosphere and simultaneously exposed to ultraviolet radiation. The interface charge is determined by the modified builtin potential derived from capacitance–voltage characteristics of Schottky contacts formed on the epilayers. The interface charge density is reduced from a typical value of ∼1×1012 cm−2 to a practically negligible value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353316
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  • 2
    Electronic Resource
    Electronic Resource
    A model for the determination of the solid composition of ternary III-V and II-VI metalorganic chemical vapor deposition epilayers (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 871-873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple kinetic model for the metalorganic chemical vapor deposition growth of ternary III-V and II-VI epilayers denoted by AxC1−xB, is presented. The model yields the relationship between the solid composition x of the epilayer and the gas-phase concentrations of the constituents in various limiting cases. The solid composition x is given by x=(1+α−1×CGMC/CGMA)−1 =[1+α−1(1−Z−1)]−1 where α is a fitting parameter determined by the process parameters, CGMA and CGMC are the gas-phase concentrations of the metalorganic sources of A and C, respectively. The gas-phase composition Z is defined by Z=CGMA/(CGMA +CGMC). The predictions of the model are compared with measured data. The data points are calculated with one fitting parameter α, indicating the validity of the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346773
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  • 3
    Electronic Resource
    Electronic Resource
    Band diagram of a HgTe-CdTe semimetal-semiconductor abrupt heterostructure (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4473-4483 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy-band diagram and interface potentials at a HgTe-CdTe abrupt heterostructure are presented. An analytic approximation is formulated and compared to an exact (numeric) calculation of the interface potentials. The error introduced by the analytic approximation is negligible for a wide range of doping levels of the CdTe. The analysis predicts that HgTe forms ohmic contacts to p-type CdTe and rectifying junctions to n-type CdTe. Interface charges above 1012 cm−2 modify the interface potentials. Positive interface charge imposes depletion in p-type CdTe resulting in potential barriers that may degrade the ohmic properties of the contacts. The methodology presented in this study may be extended to additional semimetal-semiconductor heterostructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352787
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the interface charge between an epilayer and a substrate using capacitance-voltage measurements (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 318-325 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is presented for the measurement of the interface charge between an epitaxial layer and a substrate. Capacitance-voltage characteristics of Schottky contacts formed on the epilayer are measured and analyzed. The interface charge is determined by the modified built-in potential and capacitance. Experimental results are reported for p-type CdTe epilayers grown by metalorganic chemical vapor deposition on a p-type CdTe substrate using indium contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350709
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  • 5
    Electronic Resource
    Electronic Resource
    Shockley–Read recombination and trapping in p-type HgCdTe (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3405-3412 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The concepts and definitions of the steady-state minority-carrier lifetime, the steady-state majority-carrier lifetime, and the transient excess-carrier lifetime in semiconductors are reviewed. The effects that Shockley–Read centers have on these lifetimes are discussed, with emphasis given to the case of p-type Hg0.775Cd0.225Te containing traps. Measurements of the excess-carrier lifetime in Hg0.775Cd0.225Te (Na∼1×1016/cm3) using various experimental techniques are then summarized in view of the above definitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346346
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  • 6
    Electronic Resource
    Electronic Resource
    Statistical modeling of the spectral performance of a two-dimensional array of gamma-ray spectrometers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3384-3397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We develop a statistical model for the calculation of the spectral performance of two-dimensional (2D) array of gamma-ray spectrometers. We consider a nonuniform field in the device, determined by the geometrical design of the anodes. The induced charge is calculated by solving the Poisson's equation with the appropriate boundary conditions. Furthermore, the presented model simultaneously considers a random point of photon absorption and a random drift length for each carrier, taking into account the effect of multiple trapping and detrapping. The model developed in this article enables the optimal geometrical design of the 2D array of anodes according to the electrical properties of the given semiconductor material, in order to achieve optimal results for the spectral performances. The model consists of three parts. The first is the calculation of the potential at each point of a three-dimensional (3D) map of the device. The second is the calculation of the charge induced on the anode by a point charge positioned in the device (for each point of a 3D map). The third is the statistical calculation of the pulse height spectrum. Finally, the pulse height spectrum is calculated as a function of the geometrical design, photon energy, electron and hole mobility, lifetime, mean detrapping time and applied voltage as well as the shaping time. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1432769
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of the geometrical parameters on the electric field of pixelated two-dimensional arrays of γ-ray spectrometers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5388-5394 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the effect of the geometrical parameters of pixelated two-dimensional (2D) arrays of γ-ray spectrometers upon the distribution of the electric field lines, which are induced by the applied voltage. It is shown that the size and in particular the separation between anodes strongly affect the field uniformity. The electric field is calculated by three methods including: (i) a commercial software for 3D field analysis based on finite element method; (ii) a 3D finite difference approach; and (iii) the Moments method. The required boundary conditions and the calculation efficiency of each method are compared. Since the uniformity of the electric field strongly affects the spectral performance of pixelated 2D arrays of γ-ray spectrometers, the results presented here are important for the optimal design and modeling of such arrays. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1314308
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  • 8
    Electronic Resource
    Electronic Resource
    Statistical modeling of charge collection in semiconductor gamma-ray spectrometers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 8-15 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge collection efficiency and the variance of the collected charge of semiconductor gamma-ray spectrometers are analytically modeled for the case of a uniform electric field. The model is based on a rigorous statistical approach. In contrast to previously reported models for the variance of the collected charge, the present statistical model simultaneously takes into account a random point of photon absorption (i.e., a nonuniform absorption) and a random drift time for each generated carrier. Analytical expressions are obtained for the variance of the collected charge as a function of photon energy, applied bias voltage, electron and hole mobility-lifetime products, and the direction of irradiation. Since at present the performance of high-Z room-temperature spectrometers is mainly limited by the charge transport properties of the semiconductors, it is interesting to calculate the limit for the expected resolution. The statistical model presented here yields physical insight and determines quantitatively the expected spectrometer resolution as a function of the semiconductor transport parameters and device parameters, as well as the radiation parameters. Several limiting cases are calculated and discussed. The methodology presented here, which is based on conditional probabilities, can be extended to spectrometers with nonuniform fields. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369425
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  • 9
    Electronic Resource
    Electronic Resource
    Barrier formation at graded HgTe/CdTe heterojunctions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5083-5088 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical calculations of graded HgTe/CdTe heterojunction (HJ) band diagrams at equilibrium are presented and discussed. The calculations are performed in the entire compositional range (0〈x〈1), using a nonparabolic conduction band and Fermi-Dirac statistics. The dependence of barrier formation at graded HJs are examined as a function of the graded region width and the graded region doping profiles. The graded region width and doping profiles were found to be the two main factors that determine whether barriers are formed as well as their shape and magnitude. The calculated results indicate that epitaxial ohmic HgTe contacts to extrinsic CdTe are possible, provided that the graded region is wider than one micron, and that it has the same doping type as the doping of the substrate with equal or higher absolute value. Further numerical calculations take into consideration the possible existence of distributed interface charges in the graded region of the HJ. It is shown that by assuming a classical transport over the potential barrier, the effective graded interface charge can be determined from the zero bias differential resistance of the HJ. Experimental transport measurements of metalorganic chemical vapor deposition (MOCVD) grown HgTe/p-CdTe graded HJs show a varying degree of rectification, indicating variations in the graded interface charge distributions which result from different MOCVD growth conditions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363487
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  • 10
    Electronic Resource
    Electronic Resource
    An analytical approximation for the free electron density of the Hg1−xCdxTe alloy system for 0〈x〈1 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5845-5847 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical approximation for the electron density in the conduction band of the entire Hg1−xCdxTe (MCT) alloy system (0〈x〈1) as a function of the composition, temperature and Fermi energy location, is proposed. A hyperbolic expression for the conduction band is shown to yield an error which is practically not larger than Kane's model in the entire composition range of MCT. The analytical approximation is compared with a numeric calculation of the Fermi-Dirac integral using this hyperbolic band approximation, and shows a deviation of a few percents for temperatures in the range 2〈T〈300[K], compositions in the entire range 0〈x〈1 and electron densities up to n=1020[cm−3]. This analytical approximation can be extremely useful for numerical band diagram and transport simulations of graded and abrupt MCT heterojunctions and devices. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360735
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