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4 Nov 2002

Volume 81, Issue 19, pp. 3519-3685

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Atomic relocation processes in impurity-free disordered p-GaAs epilayers studied by deep level transient spectroscopy

P. N. K. Deenapanray, A. Martin, S. Doshi, H. H. Tan, and C. Jagadish

Appl. Phys. Lett. 81, 3573 (2002); http://dx.doi.org/10.1063/1.1519728 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2002

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We have used capacitance–voltage and deep level transient spectroscopy techniques to study the relocation of impurities, such as Zn and Cu, in impurity-free disordered (IFD) p-type GaAs. A four-fold increase in the doping concentration is observed after annealing at 925 °C. Two electrically active defects HA (EV+0.39 eV) and HB2 (EV+0.54 eV), which we have attributed to Cu- and Asi/AsGa-related levels, respectively, are observed in the disordered p-GaAs layers. The injection of gallium vacancies causes segregation of Zn dopant atoms and Cu towards the surface of IFD samples. The atomic relocation process is critically assessed in terms of the application of IFD to the band gap engineering of doped GaAs-based heterostructures. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.S- Impurities in crystals
61.72.uj III-V and II-VI semiconductors

Electron transport through strongly coupled AlInP/GaInP superlattices

R. E. Martínez, I. Appelbaum, C. V. Reddy, R. Sheth, K. J. Russell, V. Narayanamurti, J.-H. Ryou, U. Chowdhury, and R. D. Dupuis

Appl. Phys. Lett. 81, 3576 (2002); http://dx.doi.org/10.1063/1.1519350 (3 pages)

Online Publication Date: 28 October 2002

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Using ballistic-electron-emission spectroscopy, electron transport through the principal (Γc,Lc) miniband of an (Al0.5In0.5P)11/(Ga0.5In0.5P)10 superlattice in the strong-coupling regime has been observed. Second derivative spectra of experimental data and Monte Carlo simulations were in agreement. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.Cd Superlattices

Scanning Kelvin force microscopy imaging of surface potential variations near threading dislocations in GaN

J. W. P. Hsu, H. M. Ng, A. M. Sergent, and S. N. G. Chu

Appl. Phys. Lett. 81, 3579 (2002); http://dx.doi.org/10.1063/1.1519732 (3 pages) | Cited 22 times

Online Publication Date: 28 October 2002

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Scanning Kelvin force microscopy is applied to study the charge nature of threading dislocations on GaN surfaces. On the oxidized surface, the surface potential maps show little change near dislocations, indicating that if the dislocations are charged in the bulk, the charges are either screened or depleted due to band bending. After cleaning in hot H3PO4, the potential near dislocations located at domain boundaries and inside domains is found to be lower, consistent with excess local negative fixed charges. Curiously, no contrast was seen for the screw dislocations at the centers of growth spirals even after H3PO4 treatment. Thus, either these screw dislocations have no gap states, or if they do have gap states, the positions are higher in energy (closer to conduction band edge) than the gap states of other dislocations. © 2002 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.37.Ps Atomic force microscopy (AFM)
73.25.+i Surface conductivity and carrier phenomena
71.55.Eq III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

Reduction of effective dielectric constant of gate insulator by low-resistivity electrodes

Kunio Saito, Yoshito Jin, and Masaru Shimada

Appl. Phys. Lett. 81, 3582 (2002); http://dx.doi.org/10.1063/1.1519736 (3 pages) | Cited 9 times

Online Publication Date: 28 October 2002

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On metal–oxide–semiconductor capacitors, the effective dielectric constant (keff) values extracted from high-frequency capacitance–voltage measurements were found to decrease when gate electrodes of very low resistivity were used. The equivalent-oxide thickness increase reaches about 1 nm with the low-resistivity electrodes. We examined gate insulators of SiO2, Al2O3, and HfO2 and gate electrodes of Al, TiN, Au, Cr, and TaN. The equivalent-oxide thickness increase can be prevented by inserting a high-resistivity metal film only 0.3 nm thick between the very low-resistivity metal and the insulator. The present results suggest that keff is reduced by the screening of ionic insulators with free electrons of the metal due to a quantum effect. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.23.-b Electronic transport in mesoscopic systems

Contactless measurement of electrical conductivity of semiconductor wafers using the reflection of millimeter waves

Yang Ju, Kojiro Inoue, Masumi Saka, and Hiroyuki Abé

Appl. Phys. Lett. 81, 3585 (2002); http://dx.doi.org/10.1063/1.1520339 (3 pages) | Cited 11 times

Online Publication Date: 28 October 2002

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We present a method for quantitative measurement of electrical conductivity of semiconductor wafers in a contactless fashion by using millimeter waves. A focusing sensor was developed to focus a 110 GHz millimeter wave beam on the surface of a silicon wafer. The amplitude and the phase of the reflection coefficient of the millimeter wave signal were measured by which electrical conductivity of the wafer was determined quantitatively, independent of the permittivity and thickness of the wafers. The conductivity obtained by this method agrees well with that measured by the conventional four-point-probe method. © 2002 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
85.30.De Semiconductor-device characterization, design, and modeling
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Measurements of anisotropic thermoelectric properties in superlattices

B. Yang, W. L. Liu, J. L. Liu, K. L. Wang, and G. Chen

Appl. Phys. Lett. 81, 3588 (2002); http://dx.doi.org/10.1063/1.1515876 (3 pages) | Cited 43 times

Online Publication Date: 28 October 2002

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Thermoelectric properties, i.e., thermal conductivity, electrical conductivity, and the Seebeck coefficient, have been measured in the directions parallel (in-plane) and perpendicular to the interface of an n-type Si(80 Å)/Ge(20 Å) superlattice. A two-wire 3ω method is employed to measure the in-plane and cross-plane thermal conductivities. The cross-plane Seebeck coefficient is deduced by using a differential measurement between the superlattice and reference samples and the cross-plane electrical conductivity is determined through a modified transmission-line method. The in-plane thermal conductivity of the Si/Ge superlattice is 5–6 times higher than the cross-plane one, and the electrical conductivity shows a similar anisotropy. The anisotropy of the Seebeck coefficients is smaller in comparison to electrical and thermal conductivities in the temperature range from 150 to 300 K. However, the cross-plane Seebeck coefficient rises faster with increasing temperature than that of the in-plane direction. © 2002 American Institute of Physics.
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73.63.-b Electronic transport in nanoscale materials and structures
72.20.Pa Thermoelectric and thermomagnetic effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
73.50.Lw Thermoelectric effects

Location of holes in silicon-rich oxide as memory states

I. Crupi, S. Lombardo, E. Rimini, C. Gerardi, B. Fazio, and M. Melanotte

Appl. Phys. Lett. 81, 3591 (2002); http://dx.doi.org/10.1063/1.1520340 (3 pages) | Cited 2 times

Online Publication Date: 28 October 2002

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The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO2 layers [used as gate dielectric in a metal–oxide–semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh time compared to conventional dynamic random access memory cells. © 2002 American Institute of Physics.
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84.30.Sk Pulse and digital circuits
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Ground state splitting of vertically stacked indium arsenide self-assembled quantum dots

Shuwei Li and Kazuto Koike

Appl. Phys. Lett. 81, 3594 (2002); http://dx.doi.org/10.1063/1.1515365 (3 pages) | Cited 2 times

Online Publication Date: 28 October 2002

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An attractive feature of vertically stacked InAs/AlGaAs quantum dots (QDs), which were buried in AlGaAs high potential barrier and spacer epilayer and grown by molecular-beam epitaxy with size-controlled growth, exhibits an unknown macroscopic quantum phenomenon (i.e., phase-change splitting of the ground state). In the vertically aligned QDs, due to many-body effect and quantum-mechanical renormalization, the electron ground state splits into a series of peaks of which the intensity gradually, systematically decreases to redshift direction with a wavelength constant. By the way, energy levels of electrons and holes might really be “seen” by deep level transient spectroscopy to which the photoluminescence experiment is in an excellent agreement. © 2002 American Institute of Physics.
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81.07.Ta Quantum dots
81.16.Dn Self-assembly
78.67.Hc Quantum dots
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