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1 Mar 2002

Volume 91, Issue 5, pp. 2563-3485

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Electrical properties of pn junctions formed by plasma enhanced epitaxial growth

Sean G. Reidy, Walter J. Varhue, Ed Adams, and Mark Lavoie

J. Appl. Phys. 91, 2984 (2002); http://dx.doi.org/10.1063/1.1436559 (5 pages) | Cited 3 times

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Properly functioning pn junction diodes have been fabricated by a low temperature plasma enhanced chemical vapor deposition (PECVD) technique. The diodes were constructed such that the metallurgical junction was coincident with the starting substrate surface. The electrical quality of the diodes was quantified by measuring their reverse bias leakage current. Contrary to popular opinion, it has been shown that the PECVD process is inherently capable of producing device quality material, and rather it is the in situ plasma cleaning technique typically associated with this method that is the cause of poor electrical performance. The chemical and physical nature of defects caused by the plasma cleaning step have been investigated by various experimental techniques including photoluminescence, secondary ion mass spectroscopy, and atomic force microscopy. The plasma cleaning step has been linked in certain cases to the production of a photoluminescence signal in Czochralski grown Si wafers. Results show that the plasma clean is neither required nor desired in the low temperature growth of device quality epitaxial Si thin films. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Current–voltage characteristics of polar heterostructure junctions

Madhusudan Singh, Jasprit Singh, and Umesh Mishra

J. Appl. Phys. 91, 2989 (2002); http://dx.doi.org/10.1063/1.1434542 (5 pages) | Cited 8 times

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We report calculations that show that a metal–polar semiconductor heterostructure can exhibit highly controllable nonlinear current–voltage characteristics. A change in barrier thickness can alter the characteristics from Schottky-like to ohmic in different bias regimes. The origin of these unusual effects is a large electric field (>106 V/cm) and high sheet charge(∼1013–1014cm−2) without doping, in the polar heterostructure. Theoretical calculation of the tunneling current density in these systems is done in this work. The results indicate that very interesting nonlinear behavior is shown by these systems, even in the undoped case. The choice of suitable compositions of the materials and thicknesses can be used to tailor devices with desired characteristics. © 2002 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions

Impurity effect on charge-ordered and ferromagnetic–metallic state in manganese perovskites: Comparison between Cr and Al doping

K. Takenaka, S. Okuyama, R. Shiozaki, T. Fujita, and S. Sugai

J. Appl. Phys. 91, 2994 (2002); http://dx.doi.org/10.1063/1.1432477 (4 pages) | Cited 4 times

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The role of impurities in melting of the charge-ordered (CO) state in half-doped manganese perovskites is discussed based on the systematic study of Cr and Al doping on the CO state as well as on the ferromagnetic–metallic (FM) state. The CO state in Nd0.5Sr0.5MnO3 is destroyed and the FM state is restored by 2% high-spin (S=3/2) Cr3+, whereas the CO state survives doping of spinless Al3+. On the other hand, the doping effects on the FM state in La1−xSrxMnO3 are almost identical between Cr and Al, except that Cr degrades Curie temperature less. The slight resistance of the CO state against Cr doping can be explained by the magnetic interaction between the Cr and the Mn t2g spins. © 2002 American Institute of Physics.
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75.30.Hx Magnetic impurity interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
71.45.-d Collective effects

Properties of a hole trap in n-type hexagonal GaN

P. Muret, A. Philippe, E. Monroy, E. Muñoz, B. Beaumont, F. Omnès, and P. Gibart

J. Appl. Phys. 91, 2998 (2002); http://dx.doi.org/10.1063/1.1433935 (4 pages) | Cited 19 times

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Minority carrier transient spectroscopy is performed in Schottky diodes fabricated on hexagonal n-type GaN grown by metalorganic chemical vapor deposition, either doped with two concentrations of Si or unintentionally doped. Capacitance transients are measured after a light pulse sent through the semitransparent contact which generates electron–hole pairs in the depletion zone. They display the characteristic sign of hole emission. The same deep level is detected in all the samples, independent of the doping level and doping species, with a concentration of some 1015 cm−3, even in the sample prepared by epitaxial lateral overgrowth. The ionization energy and capture cross section deduced from Fourier Transform transient spectroscopy are respectively 0.81±0.03 eV and 2×10−14 cm2. Such a capture cross section for holes indicates an attractive potential and hence a negatively charged center before the hole capture. Hole emission is suppressed by electron–hole recombination when a sufficiently long majority carrier pulse is applied after the light pulse. A single recombination time constant is measured and an electron capture cross section near 10−21 cm2, independent of temperature, is deduced. These facts demonstrate that this deep center is a point defect, still negatively charged after a hole has been captured, since it repels electrons, and hence it is a deep acceptor. All these properties fit very well the theoretical predictions previously published about the isolated gallium vacancy in n-type GaN. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Confirmation of the pyroelectric coefficient of strained InxGa1−xAs/GaAs quantum well structures grown on (111)B GaAs by differential photocurrent spectroscopy

J. J. Sánchez, J. I. Izpura, J. M. G. Tijero, E. Muñoz, Soohaeng Cho, and A. Majerfeld

J. Appl. Phys. 91, 3002 (2002); http://dx.doi.org/10.1063/1.1445278 (5 pages) | Cited 4 times

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In this work we used the differential photocurrent technique to measure the strain-induced piezoelectric field in pseudomorphic InxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy on (111)B GaAs substrates. Single and multiple quantum well p–i–n diodes with two different In fractions in the well were analyzed in the temperature range of 25–300 K. Our results for a sample with a 17% In fraction confirm the previously reported value of the pyroelectric coefficient for a similar sample obtained by photoreflectance spectroscopy, hence, the equivalence of the differential photocurrent and photoreflectance techniques is also demonstrated. For a sample with 21% In, we report experimental determination of the temperature dependence of the piezoelectric constant and, therefore, of the strain-induced component of the pyroelectric coefficient. © 2002 American Institute of Physics.
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77.70.+a Pyroelectric and electrocaloric effects
73.63.Hs Quantum wells
77.65.Ly Strain-induced piezoelectric fields
73.50.Pz Photoconduction and photovoltaic effects
77.65.Bn Piezoelectric and electrostrictive constants
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Shock wave demagnetization of BaFe12O19 hard ferrimagnetics

S. I. Shkuratov, E. F. Talantsev, J. C. Dickens, and M. Kristiansen

J. Appl. Phys. 91, 3007 (2002); http://dx.doi.org/10.1063/1.1431434 (3 pages) | Cited 12 times

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A study of the effect of shock waves on the phase state of a hard ferrimagnetic material has been performed. A plane shock wave was passed along the axis of a cylindrical BaFe12O19 hard ferrite magnet. The shock wave demagnetized the cylinder, reducing the magnetic flux. This change in magnetic flux generated an electromotive force (EMF) in a coil wound around the ferrite. The value of the EMF calculated on the assumption that the ferrite was completely demagnetized by the shock wave is in good agreement with the peak EMF value obtained experimentally. © 2002 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
62.50.-p High-pressure effects in solids and liquids
75.50.Gg Ferrimagnetics
75.50.Vv High coercivity materials

Energy level alignment and two-dimensional structure of pentacene on Au(111) surfaces

P. G. Schroeder, C. B. France, J. B. Park, and B. A. Parkinson

J. Appl. Phys. 91, 3010 (2002); http://dx.doi.org/10.1063/1.1445286 (5 pages) | Cited 93 times

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X-ray photoemission, ultraviolet photoemission spectroscopy (UPS), and scanning tunneling microscopy (STM) have been used to determine the energy level alignment and the molecular ordering of monolayer and submonolayer pentacene films on Au(111) in ultrahigh vacuum. Pentacene evaporated onto the van der Waals surface of SnS2 was used as a noninteracting substrate for comparison. A large interface dipole was measured for pentacene on Au(111) (0.95 eV) whereas pentacene on SnS2 showed a relatively small interface dipole (0.26 eV). The different interface dipoles are related to the different orientations of the pentacene molecules due to different pentacene substrate interaction energies. Differences in the UPS spectra also support changing molecular orientations of the two substrates. STM images of pentacene on Au(111) revealed that the molecules lay flat on the substrate and are oriented parallel to each other, forming striped structures that are commensurate with the Au(111) lattice. The pentacene coverage influences the packing of the striped structures that can form a variety of unit cells. Three related unit cells with pentacene molecules tilted [(2×2√7), (2×√31), and (2×√39)] or perpendicular (2×3√3) to the row direction were identified on Au(111). © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
73.20.At Surface states, band structure, electron density of states
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Determination of the occupancy level of the DX center resonant with the conduction band in Te-doped AlGaSb

C. Ghezzi, R. Magnanini, A. Parisini, S. Franchi, E. Gombia, and R. Mosca

J. Appl. Phys. 91, 3015 (2002); http://dx.doi.org/10.1063/1.1445495 (6 pages) | Cited 1 time

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The analysis of the amplitude of the deep level transient spectroscopy signal due to DX centers is exploited to determine the EDX occupancy level of the DX center in Te-doped AlxGa1−xSb in the range of low values of x where EDX is resonant with the conduction band. We take advantage of a small but still detectable change in the occupancy factor of the DX level induced by the filling pulse. It is shown that EDX is very close to the L conduction band edge for x⩽0.20. This behavior is different from the one at x⩾0.30 where EDX lies in the forbidden energy gap and exhibits an x dependence similar to the X edge. These results are discussed at the light of different atomic configuration for DX centers at an anion-substitutional impurity. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds

Electronic defect studies of ladder-type polymers

A. A. Alagiriswamy and K. S. Narayan

J. Appl. Phys. 91, 3021 (2002); http://dx.doi.org/10.1063/1.1445279 (7 pages) | Cited 6 times

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Electrically active defects have a profound impact on the semiconducting properties of conjugated polymer systems. Defect-induced thermally stimulated current (TSC) in poly (benzimadazobenzophenanthroline), a ladder-type, high-temperature conjugated polymer, is studied in detail. The TSC results identify the nature and the energetics of the trap levels in the polymer. Variations in the results as a function of the initial trap-filling parameters and the thermal history were also observed. The long-lived component in the photoinduced current decay, an indicator of defect states, is also studied within this context. The barrier limiting processes of the photocurrent are correlated with the results obtained from TSC measurements and we speculate on the origin of these defects. © 2002 American Institute of Physics.
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71.55.Jv Disordered structures; amorphous and glassy solids
72.40.+w Photoconduction and photovoltaic effects
72.80.Le Polymers; organic compounds (including organic semiconductors)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Resonant electromagnetic field cavity between scanning tunneling microscope tips and substrate

P. André, F. Charra, and M. P. Pileni

J. Appl. Phys. 91, 3028 (2002); http://dx.doi.org/10.1063/1.1447325 (9 pages) | Cited 8 times

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Confined electromagnetic fields are created at the surface of various substrates such as indium-tin-oxide (ITO) and gold films. Two scanning tunneling microscope tips (Pt–Ir and W) are used to create a localized perturbation. With ITO as a substrate, an evanescent field is observed without a tip-substrate interaction. Conversely, with a gold film surface formation of “gap modes,” the particle-substrate cavity is seen. Gap modes at the interface of a metallic film are involved essentially when the modulation amplitude of the particle is below 100 nm. In the context of apertureless near-field microscopy, this demonstrates the influence of tip-surface coupling in scanning plasmon near-field microscope (SPNM) signals. The strong interaction of the tip with the metal substrate, through its surface plasmon, when combined with SPNM, may result in inaccuracies in the claimed chemical identification or intrinsic optical properties of the particle. © 2002 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Simulation of the charge transport across grain boundaries in p-type SrTiO3 ceramics under dc load: Debye relaxation and dc bias dependence of long-term conductivity

Th. Hölbling and R. Waser

J. Appl. Phys. 91, 3037 (2002); http://dx.doi.org/10.1063/1.1448404 (7 pages) | Cited 9 times

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A mathematical-physical model to describe the charge transport across grain boundaries in p-type SrTiO3 ceramics in the low-temperature regime for arbitrary dc voltage steps has been developed. The finite element model structure consists of a one-dimensional cross section through a ceramic scenario. Mathematical formulation comprises a coupled system of continuity equations (utilizing Maxwell-Boltzmann transport equations) and Poisson’s equation, with the appropriate boundary conditions for a potentiostatic simulation approach. The edges of the model are assumed to be blocking for ionic transport, and penetrable for electronic transport. The model was implemented exploiting routines from the numerical class library DIFFPACK™. After an initial electrostatic simulation a dc bias voltage step is applied. The evolution of the spatial profiles of electric potential, defect concentrations, space-charge density, and electric conductivity, and the current response are calculated. The results for the ceramic model structure confirm the experimentally observed Debye relaxation, and the characteristic dependence of long-term conductivity on the dc bias after space-charge polarization, before the onset of resistance degradation. © 2002 American Institute of Physics.
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72.60.+g Mixed conductivity and conductivity transitions
72.80.Jc Other crystalline inorganic semiconductors
77.22.Gm Dielectric loss and relaxation
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.72.Mm Grain and twin boundaries
66.30.H- Self-diffusion and ionic conduction in nonmetals
77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ej Polarization and depolarization

Magnetoresistive effect in p-type semiconducting diamond films

C. Y. Kong, W. L. Wang, K. J. Liao, S. X. Wang, L. Fang, and Y. Ma

J. Appl. Phys. 91, 3044 (2002); http://dx.doi.org/10.1063/1.1446662 (5 pages) | Cited 1 time

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Magnetoresistive effects were studied in p-type heteroepitaxial diamond films with a strip or Corbino disk structure in a magnetic field ranging from 0 to 5 T. The films were grown by microwave plasma chemical vapor deposition and boron doped by cold ion implantation and rapid thermal annealing. The experimental results show that the magnetoresistance (MGR) of p-type heteroepitaxial diamond films strongly depends on the geometric form of the samples and the magnetic field. Diamond films are assumed to be an isotropic isothermal solid in which conduction is by holes from light, heavy and split-off bands. Based on the Fuchs and Sondheimer thin-film theory, considering spherical energy surfaces and mixed scattering by lattice vibrations and ionized impurities and surface, a theoretical description of the magnetoresistive effect in diamond films is presented by solving the Boltzmann transport equation in the relaxation time approximation. A relationship between the MGR and the thickness of films, magnetic field, and mobility is shown. © 2002 American Institute of Physics.
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73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.up Other materials
81.05.U- Carbon/carbon-based materials
81.05.Cy Elemental semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
63.20.-e Phonons in crystal lattices

Simulation of characteristics of a molecular single-electron tunneling transistor with a discrete energy spectrum of the central electrode

V. V. Shorokhov, P. Johansson, and E. S. Soldatov

J. Appl. Phys. 91, 3049 (2002); http://dx.doi.org/10.1063/1.1435832 (5 pages) | Cited 6 times

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Current–voltage curves of molecular single-electron tunneling transistors are simulated based on a modified theory of single electronics that accounts for the discreteness of the energy spectrum of the molecule. The simulation was performed including effects of energy relaxation of the electrons in the molecule for two limiting cases of fast and slow relaxation, and for both equidistant and randomly spaced energy levels of the molecule. An efficient recursion method allowing a fast calculation of the Gibbs canonical distribution for electrons in the molecule is suggested and realized. A comparison of the simulated I–V curves with the experimental ones shows that the experimental conditions correspond to the slow relaxation case. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
85.65.+h Molecular electronic devices
73.23.Hk Coulomb blockade; single-electron tunneling
73.20.At Surface states, band structure, electron density of states

Bound state of the quantum dot formed at intersection of L- or T-shaped quantum wire in inhomogeneous magnetic field

Yuh-Kae Lin, Yueh-Nan Chen, and Der-San Chuu

J. Appl. Phys. 91, 3054 (2002); http://dx.doi.org/10.1063/1.1446233 (8 pages) | Cited 3 times

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A quantum dot (QD) can be formed at the intersection of the symmetric or asymmetric L-shaped (LQW) or T-shaped quantum wire (TQW). The bound state energies in such QD systems surrounded by inhomogeneous magnetic fields are found to depend strongly on the asymmetric parameter α=W2/W1, i.e., the ratio of the arm widths and magnetic field applied on the wire arms. Two effects of the magnetic field on the bound state energy of the electron can be obtained. One is the depletion effect which purges the electron out of the QD system. The other is to create an effective potential due to the quantized Landau levels of the magnetic field. Depletion effect is found to be more prominent in weak field region. Our results show the bound state energy of the electron in such QD system depends quadratically (linearly) on the magnetic field in the weak (strong) field region. It is also found that the bound state energy of the electron depends on the magnetic field strength only and not on its direction. A simple model is proposed to explain the behavior of the magnetic dependence of the bound state energy of the electron both in weak and strong magnetic field regions. The contour plots of the relative probability of the bound state in LQW or TQW in magnetic field are also presented. © 2002 American Institute of Physics.
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73.21.La Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)

Characterization of the bonding strength and interface current of p-Si/n-InP wafers bonded by surface activated bonding method at room temperature

M. M. R. Howlader, T. Watanabe, and T. Suga

J. Appl. Phys. 91, 3062 (2002); http://dx.doi.org/10.1063/1.1430883 (5 pages) | Cited 10 times

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Bonding between p-Si and n-InP was performed through the surface activated bonding method at room temperature. Tensile results show that the samples were visibly separated from the bonded interface, indicating a weak bonding strength. The cause of the weak bonding strength was intensively investigated. Consistent results between x-ray photoelectron spectroscopy and atomic force microscope investigations show that a weak phase of indium is terminated on the InP due to the depletion of phosphorus in the sputtered surface. Existence of indium layers on the debonded Si surface indicate that the samples were separated from the interface of In/InP, but not across the bonded interface of Si and indium. Typical pn junction current–voltage behavior indicates no high resistance interface layer that can withstand the flow of current through the interface. Remarkably, sputtering time as well as energy dependence on the interface current is found to be due to the accumulation of sputtering induced defects. © 2002 American Institute of Physics.
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81.65.Ps Polishing, grinding, surface finishing
79.60.Jv Interfaces; heterostructures; nanostructures
68.35.Np Adhesion
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Multiple subband transitions and evidence for population inversion in InAs/In(As,Sb) heterostructures

J. D. Heber, H. R. Hardaway, X. Li, M. J. Pullin, and C. C. Phillips

J. Appl. Phys. 91, 3067 (2002); http://dx.doi.org/10.1063/1.1445493 (7 pages)

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We report on improved InAs/InAs1−xSbx heterostructure single quantum well emitters for the mid-infrared wavelength region. An InAlAs barrier layer has been incorporated into the active region of the structures for improved electron confinement. With room temperature pulsed power outputs of 140 μW at a wavelength of 4.3 μm, an improvement of more than a factor of 6 has been achieved compared to similar structures without the barrier layer. Magneto-electroluminescence measurements at 4 K reveal the presence of multiple subband transitions in the spectra. Based on a k⋅p model assuming a type-IIa band offset, these transitions are identified as (e1,hh1) and (e1,lh1). The observation of these multiple transitions is shown to be strong evidence for population inversion in the structures. © 2002 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
81.07.St Quantum wells
42.50.-p Quantum optics
78.60.Fi Electroluminescence
78.20.Ls Magneto-optical effects
71.15.-m Methods of electronic structure calculations
71.20.Nr Semiconductor compounds

Electronic structure and optical properties of SrCu2O2

Hiromichi Ohta, Masahiro Orita, Masahiro Hirano, Iwao Yagi, Kazushige Ueda, and Hideo Hosono

J. Appl. Phys. 91, 3074 (2002); http://dx.doi.org/10.1063/1.1445498 (5 pages) | Cited 19 times

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The electronic structure of SrCu2O2, a wide gap (∼3.3 eV) p-type oxide semiconductor, was examined by photoelectron and optical spectroscopy. The spectroscopy results were compared with the energy band structure calculated by the local density approximation method to clarify the origins of p-type conductivity in this material. Despite the significant difference in band gap energy, the basic electronic structure around the band gap region was found to be quite similar to that of Cu2O. Thus, the 3d−4sp orbital of Cu+ ion is hybridized with the 2p orbital of ligand O2− ions due to the covalency of Cu–O bonds, to form states near the valence band maximum; the conduction band minimum is predominantly composed of the hybridized orbital of Cu 4sp and O 2p, forming the direct band gap at Γ point. A sharp absorption band observed near the fundamental absorption edge is likely attributable to an exciton. Although the corresponding exciton emission was not observed near the absorption edge, a blue-green emission band (Stokes shift of ∼1 eV) was observed at ∼2.47 eV. The emission is presumably attributable to intra-atomic transitions of Cu+, partially allowed by p-orbital mixing into s and d orbitals. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
81.05.Hd Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.40.Fy Semiconductors
71.35.-y Excitons and related phenomena

Band alignments in metal–oxide–silicon structures with atomic-layer deposited Al2O3 and ZrO2

V. V. Afanas’ev, M. Houssa, A. Stesmans, and M. M. Heyns

J. Appl. Phys. 91, 3079 (2002); http://dx.doi.org/10.1063/1.1436299 (6 pages) | Cited 80 times

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The energy barrier height Φ for electrons at the interfaces of various metals (Mg,Al,Ni,Cu,Au) with nanometer-thin Al2O3 and ZrO2 layers grown on (100)Si by atomic layer deposition has been directly measured using internal photoemission of electrons into the insulator. The behavior of the metal/Al2O3 contacts with increasing metal electronegativity XM resembles that of the metal/SiO2 interfaces with ideality factor dΦ/dXM≈1. The metal/ZrO2 contacts exhibit a less ideal behavior with dΦ/dXM≈0.75. The metal–silicon work function differences in structures with Al2O3 and ZrO2 insulators appear to be considerably larger than in the structures with thermally grown SiO2, suggesting the presence of a negative dipole layer at the metal/deposited oxide interface. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Jv Interfaces; heterostructures; nanostructures

Surface relaxation effects on the properties of porous silicon

E. Vázquez, J. Tagüeña-Martínez, L. E. Sansores, and C. Wang

J. Appl. Phys. 91, 3085 (2002); http://dx.doi.org/10.1063/1.1446658 (5 pages) | Cited 8 times

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In this article, surface relaxation and its effects on the electronic and structural properties of porous silicon are studied by using the total-energy pseudopotential formalism within the density-functional theory. Our model is based on a 32-atom supercell, where columns of atoms are removed and saturated with hydrogen atoms. Samples with 4.4%, 13.6%, 16.8%, 28.9%, and 41.3% porosity are analyzed in detail. The results show a clear expansion of the system along the pore direction as the porosity increases. Moreover, this expansion is very sensitive to the hydrogen-atom concentration and a linear dependence is observed. The dependence of the band gap and the effective mass on the porosity are also analyzed. Here, the hydrogen-atom number and pore shapes are observed to play a fundamental role. © 2002 American Institute of Physics.
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71.20.Mq Elemental semiconductors
61.43.Gt Powders, porous materials
71.15.Nc Total energy and cohesive energy calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
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