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1 Jun 1998

Volume 83, Issue 11, pp. 5609-7398

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High resolution x-ray diffraction study of Bragg peak width in strained InGaAs/InAlAs/InP heterostructures

Quankui Yang, Aizhen Li, and Jianxin Chen

J. Appl. Phys. 83, 5792 (1998); http://dx.doi.org/10.1063/1.367434 (5 pages) | Cited 1 time

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Many different reflections have been investigated by high resolution x-ray diffraction on gas source molecular beam epitaxy grown strained InGaAs/InAlAs/InP heterostructures to study the Bragg peak widths. Results show that even deducting the influence of the intrinsic peak width and the influence of the instrument broadening, for either InGaAs or InAlAs epilayers, a linear relationship between the square of the Bragg peak width and tan2 θB exists with θB the Bragg angle, for either grazing incidence or grazing emergence geometry. Different slopes for the linear relationship have been measured in the two different geometries. Systematically, a much bigger peak width is detected under a grazing incidence geometry than that under a grazing emergence geometry for the same asymmetric reflection. The phenomenon is explained by the existence of a normal strain gradient along the growth direction of the epilayer’s thickness. This normal strain gradient has been confirmed by x-ray triple-axis two-dimensional mapping. Moreover, a broader peak width of the (117) reflection than that of the (155) reflection is consistent with the strain gradient. © 1998 American Institute of Physics.  
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Effects of prior hydrogenation on the structure and properties of thermally nanocrystallized silicon layers

A. Achiq, R. Rizk, F. Gourbilleau, R. Madelon, B. Garrido, A. Pérez-Rodríguez, and J. R. Morante

J. Appl. Phys. 83, 5797 (1998); http://dx.doi.org/10.1063/1.367435 (7 pages) | Cited 11 times

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Nanocrystalline silicon layers have been obtained by thermal annealing of films sputtered in various hydrogen partial pressures. The as-deposited and crystallized films were investigated by infrared, Raman, x-ray diffraction, electron microscopy, and optical absorption techniques. The obtained data show evidence of a close correlation between the microstructure and properties of the processed material, and the hydrogen content in the as-grown deposit. The minimum stress deduced from Raman was found to correspond to the widest band gap and to a maximum hydrogen content in the basic unannealed sample. Such a structure relaxation seems to originate from the so-called “chemical annealing” thought to be due to Si–H2 species, as identified by infrared spectroscopy. The variation of the band gap has been interpreted in terms of the changes in the band tails associated with the disorder which would be induced by stress. Finally, the layers originally deposited with the highest hydrogen pressure show a lowest stress—which does not correlate with the hydrogen content and the optical band gap—and some texturing. These features are likely related to the presence in these layers of a significant crystalline fraction already before annealing. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.Am Elemental semiconductors and insulators
61.72.Cc Kinetics of defect formation and annealing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Db Elemental semiconductors and insulators
68.60.Dv Thermal stability; thermal effects

Dose- and annealing-induced changes in the microstructure of buried SiNx: An x-ray absorption study

E. C. Paloura

J. Appl. Phys. 83, 5804 (1998); http://dx.doi.org/10.1063/1.367436 (6 pages) | Cited 2 times

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The microstructure and the annealing behavior of N-rich SiNx films are studied with x-ray absorption measurements at the N-K edge. The SiNx films were fabricated with ion implantation of 35 keV N+ ions into Si substrates, in the dose range 2×1017–2×1018 ions/cm2. The near-edge x-ray absorption fine structure (NEXAFS) spectra of the N-rich films are characterized by a strong resonance line (RL2) at 403.3±0.1 eV whose intensity increases with the implantation dose. RL2 is attributed to dipole electron transitions, from 1s to unoccupied p orbitals, at a defect site containing a N dangling bond defect. The defect related to RL2 has high thermal stability and is practically unaffected by vacuum annealing up to 1000 °C. One more defect-related resonance (RL1) is detected at 401.1±0.3 eV in the films fabricated with the lower and intermediate used implantation doses (2×1017 and 1×1018 cm−2, respectively). The activation energy for the annealing of RL1 is 0.50±0.05 eV. Extended x-ray absorption fine structure spectroscopy (EXAFS) on the as-implanted and annealed films reveals that subnitrides are formed upon implantation. These nitrides are characterized by a Si-N nearest-neighbor distance which is comparable to that of the reference nitride, while the coordination number in the first nearest-neighbor shell N1 depends on the implantation dose. The stoichiometry deviation, as measured from the value of N1 which takes values between 1.7 and 2.8 for the limiting doses of 2×1018 and 2×1017 cm−2, respectively, shows the correlation between the RL2 in the NEXAFS spectra and the presence of N dangling bonds in the as-implanted films. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.80.Jh Ion radiation effects
78.70.Dm X-ray absorption spectra
61.72.Cc Kinetics of defect formation and annealing

Lateral periodicity and elastic stress relaxation in GaInAsP quantum wires on InP investigated by x-ray diffractometry

B. Jenichen, H. T. Grahn, T. Kojima, and S. Arai

J. Appl. Phys. 83, 5810 (1998); http://dx.doi.org/10.1063/1.367437 (4 pages) | Cited 2 times

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Synchrotron x-ray diffractometry has been used to investigate GaInAsP quantum wire structures on InP with a quantum well layer between the substrate and the wire. The lateral periodicity was determined with high accuracy. An elastic stress relaxation, which occurs near the free surface of the sidewalls, was observed. It results in deformation gradients in the wires, which influence the distribution of the diffracted intensity in reciprocal space. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Thin layers and multilayers of porous silicon: X-ray diffraction investigation

D. Buttard, D. Bellet, G. Dolino, and T. Baumbach

J. Appl. Phys. 83, 5814 (1998); http://dx.doi.org/10.1063/1.367438 (9 pages) | Cited 19 times

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Porous silicon is a unique example of a porous material exhibiting the properties of a nearly perfect single crystal. High resolution x-ray diffraction has been used to investigate thin p− and p+ type porous silicon layers in the 100–1000-nm-thickness range. Since several thickness fringes are observed, the comparison between experimental results and simulations enables one to deduce information about the main structural parameters such as porosity, lattice parameter, thickness, and heterotransition width. Porous silicon multilayers have also been investigated: some satellites are clearly observed. The obtained results are then compared and discussed with the literature. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.05.cp X-ray diffraction

X-ray characterization of buried allotaxially grown CoSi2 layers in Si(100)

U. Zimmermann, J.-P. Schlomka, M. Tolan, J. Stettner, W. Press, M. Hacke, and S. Mantl

J. Appl. Phys. 83, 5823 (1998); http://dx.doi.org/10.1063/1.367439 (8 pages) | Cited 4 times

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An x-ray study of the interface morphology and lattice parameters of buried expitaxial CoSi2 layers in Si(100) is presented. Specular reflectivity, diffuse and crystal truncation rod scattering, together with grazing incidence diffraction yield detailed information about the interface quality and lattice mismatch. It turns out that the CoSi2 interfaces are considerably smoothened by an annealing step at 1150 °C. Also the in-plane correlation length of the roughness increases yielding laterally smoother interfaces. While the perpendicular lattice parameter is between that of a free relaxed and a pseudomorphic structure and a linear contraction as function of the annealing temperature is obtained, grazing incidence diffraction reveals the opposite effect for the in-plane lattice mismatch. © 1998 American Institute of Physics.
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68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments

Microstructure and properties of silicon nitride thin films deposited by reactive bias magnetron sputtering

Joo Han Kim and Ki Woong Chung

J. Appl. Phys. 83, 5831 (1998); http://dx.doi.org/10.1063/1.367440 (9 pages) | Cited 40 times

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Silicon nitride (SiNx) thin films have been deposited by radio frequency (rf) magnetron sputtering of a silicon target in reactive nitrogen-argon atmospheres without intentional substrate heating. The influence of negative substrate bias Vs on the microstructural, compositional, chemical, mechanical, and optical properties of the SiNx films was systematically investigated. An extensive analysis of the films was carried out using ellipsometry, transmission electron microscopy (TEM), atomic force microscopy (AFM), Rutherford backscattering spectrometry, secondary ion mass spectrometry (SIMS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy, stress and chemical etch rate measurements. TEM and AFM studies revealed that films produced at low bias voltages had a porous columnar structure containing large void, typical of zone 1, but that films produced at higher bias voltages had relatively smooth surfaces with a highly condensed structure, typical of zone T. Both FTIR and SIMS analyses showed that an extremely small amount of hydrogen was contained in the SiNx films deposited at Vs over −75 V, resulting from the film densification by energetic bombardment. It was also found that the amount of argon incorporated in the film increased with increasing bias voltage, whereas the oxygen content decreased. As the substrate bias voltage was increased, the mechanical internal stress in the SiNx films became increasingly compressive and saturated at a value of about 1.8×1010 dyne/cm2 at higher bias voltages. This was found to be well correlated with the increased argon content and the film densification. The lowest etch rate in buffered hydrofluoric acid, approximately 72 Å/min, was observed with the application of a substrate bias of −50 V. A further reduction in etch rate could be achieved by annealing at 900 °C for 1 h in a N2 ambient. The optical band gap of the SiNx films varied from 4.85 to 4.39 eV depending on the bias voltage. © 1998 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
78.66.Nk Insulators
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing

Spectroscopic ellipsometric study of the size evolution of Ge islands grown on Si (100)

E. Palange, L. Ragni, L. Di Gaspare, G. Capellini, and F. Evangelisti

J. Appl. Phys. 83, 5840 (1998); http://dx.doi.org/10.1063/1.367441 (5 pages) | Cited 7 times

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In this article we discuss the use of spectroscopic ellipsometry for an in situ and real time probe of three-dimensional self-organized Ge island growth on Si (100) surfaces. We will show that atomic force microscopy and x-ray photoemission spectroscopy can be combined with spectroscopic ellipsometry to give information on the size and shape evolution of the Ge islands as well as on the amount of Ge deposited on the Si surface. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Cy Elemental semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Theoretical study of antisite arsenic incorporation in the low temperature molecular beam epitaxy of gallium arsenide

S. Muthuvenkatraman, Suresh Gorantla, Rama Venkat, and Donald L. Dorsey

J. Appl. Phys. 83, 5845 (1998); http://dx.doi.org/10.1063/1.367442 (7 pages) | Cited 2 times

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A stochastic model for simulating the surface growth processes in the low temperature molecular beam epitaxy of gallium arsenide is developed, including the presence and dynamics of a weakly bound physisorbed state for arsenic. The physisorbed arsenic is allowed to incorporate into the arsenic site or gallium site (antisite) and evaporate. Additionally, the antisite As is allowed to evaporate from the surface of the crystal. The arsenic flux, temperature and growth rate dependences of antisite arsenic (AsGa) concentration and the resultant % lattice mismatch obtained from our simulation are in excellent agreement with the experimental results. The activation energy of 1.16 eV for the evaporation of antisite arsenic from the crystal obtained from our model is in good agreement with theoretical estimates. At a constant substrate temperature and growth rate (Ga flux rate), the antisite arsenic concentration and hence, the % lattice mismatch increase with arsenic flux in the low flux regime and saturate for high flux regime. The critical arsenic flux at which the AsGa concentration and the % lattice mismatch saturate, increases with temperature. The AsGa concentration and % lattice mismatch saturate at lower values for higher temperatures. As the arsenic flux increases, the coverage of the physisorbed layer increases and at a critical flux dictated by the fixed temperature and growth rate, the coverage saturates at its maximum value of unity (a complete monolayer) and hence, the concentration of AsGa and % lattice mismatch saturate. Lower AsGa concentration and % lattice mismatch result at higher temperature due to more evaporation of AsGa from the surface of the growing crystal. Additionally, an analytical model is developed to predict the AsGa concentration and % lattice mismatch for various growth conditions. © 1998 American Institute of Physics.  
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.J- Point defects and defect clusters
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena
64.70.Hz Solid-vapor transitions
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Band offsets at the InAlGaAs/InAlAs (001) heterostructures lattice matched to an InP substrate

X. H. Zhang, S. J. Chua, S. J. Xu, and W. J. Fan

J. Appl. Phys. 83, 5852 (1998); http://dx.doi.org/10.1063/1.367443 (3 pages) | Cited 2 times

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The first-principles pseudopotential method combined with virtual crystal approximation is used to calculate band offsets at the In0.53(AlzGa1−z)0.47As/In0.52Al0.48As (001) heterostructures lattice matched to an InP substrate. It is found that the valence-band offset (VBO) varies with respect to the aluminum composition as VBO = 0.18–0.16z–0.02z2 eV, while the conduction-band offset (CBO) varies as CBO = 0.51–0.33z–0.18z2 eV. Our results are in good agreement with the experimental data. © 1998 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Thermoelectric power in porous silicon

R. G. Mathur, R. M. Mehra, and P. C. Mathur

J. Appl. Phys. 83, 5855 (1998); http://dx.doi.org/10.1063/1.367444 (3 pages) | Cited 8 times

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Thermoelectric power measurements have been made on macroporous (pore width >500 Å°) porous silicon samples prepared by an anodic dissolution technique. The sign of thermopower is found to be negative indicating that conduction takes place due to electrons in the conduction band. The conduction mechanism is found to be due to variable range hopping near the Fermi level for temperatures below 150 K. At higher temperatures the conduction is due to the tunneling of carriers in the localized states in the band edges. It was concluded that these localized states are formed because the nanocrystallites in porous silicon are randomly distributed in size and orientation leading to fluctuations in band gap. This results in the constitution of a disordered system on a macroscopic scale. © 1998 American Institute of Physics.
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72.80.Cw Elemental semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
72.20.Fr Low-field transport and mobility; piezoresistance
71.55.Jv Disordered structures; amorphous and glassy solids

Electrical properties of Ga and ZnS doped ZnO prepared by mechanical alloying

B. A. Cook, J. L. Harringa, and C. B. Vining

J. Appl. Phys. 83, 5858 (1998); http://dx.doi.org/10.1063/1.367445 (4 pages) | Cited 9 times

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A series of n-type ZnO alloys doped with Ga and ZnS were prepared by mechanical alloying. Densities of 95% to 98% of theoretical density were achieved by hot pressing the milled powders at 1000 and 1200 °C, respectively. The electrical resistivity and Seebeck coefficient of alloys containing 0.25–3.0 at. % Ga were characterized between 22 and 1000 °C. The magnitude of the resistivity and Seebeck coefficient at 22 °C ranged from 0.2 mΩ cm and −25 μV/°C for the most heavily doped specimen to 1.1 mΩ cm and −70 μV/°C for the lightly doped material. The alloys exhibit a positive temperature coefficient of resistivity and Seebeck coefficient with a nearly constant slope over the temperature range studied. Thermal diffusivity measurements on a specimen containing 1.0 at. % Ga were performed over the same temperature range. The thermal conductivity appears to follow a T−1 dependence, decreasing from 180 mW/cm °C at 22 °C to 82 mW/cm °C at 1000 °C. An estimate of the maximum dimensionless thermoelectric figure of merit, ZT, in this system at 1000 °C gives a value of 0.26, a factor of three to four less than current state-of-the-art materials such as Si–Ge. A significant reduction in thermal conductivity would be required to make these alloys competitive with existing thermoelectric power generation materials. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Pa Thermoelectric and thermomagnetic effects
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Electron mobility in In0.5Ga0.5P

B. R. Nag and Madhumita Das

J. Appl. Phys. 83, 5862 (1998); http://dx.doi.org/10.1063/1.367446 (3 pages) | Cited 4 times

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The Hall mobility of electrons is calculated for In0.5Ga0.5P by using the experimental values of the effective mass and the band gap, and the estimated values of other constants. The experimental results are explained by taking the alloy scattering potential and the acoustic phonon deformation potential to be 0.435 and 12 eV, respectively. It is concluded that the experimental samples had impurity concentrations lying mostly between 5 and 15 times the electron concentration. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.20.Nr Semiconductor compounds

Electrical properties of buried B/Si surface phases

A. V. Zotov, V. G. Lifshits, T. Rupp, and I. Eisele

J. Appl. Phys. 83, 5865 (1998); http://dx.doi.org/10.1063/1.367447 (5 pages) | Cited 1 time

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Conductivity and Hall-effect measurements have been carried out at 24 K for a set of various layered structures with buried B/Si surface phases used as delta-doped layers. Evidence is found for hole mobility enhancement as a consequence of boron dopant ordering. The electrical measurements reveal a basic difference in room temperature adsorption for boron on Si(100) and Si(111) surfaces. The characterization of the samples containing buried B/Si(111) interfaces and extra-thin Ge layers suggests promise for improving the structure and electrical properties of the buried surface phases. The hole mobility in epi-Si/Ge/B/Si(111) structures is found to be about 2.5 times higher than in epi-Si/B/Si(111) samples. © 1998 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance

Charge injection and conduction on the surface of insulators

M. P. Pépin and H. J. Wintle

J. Appl. Phys. 83, 5870 (1998); http://dx.doi.org/10.1063/1.367448 (10 pages) | Cited 4 times

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We have calculated numerically the flow of charge onto an insulator surface by injection from an electrode touching the surface, using conformal mapping in conjunction with the boundary element method. We have assumed that the driving fields are due to the electrodes and to the surface charge itself, while the natural conductivity of the surface is negligible. We have considered three geometries used experimentally. In general, we find that for strong injection, the surface charge is confined to the region close to the injecting electrode, that the absorption current behaves as I∝t−γ,γ ∼ 1/3, and that the absorption and resorption currents do not exhibit mirror symmetry. Furthermore, if the active electrode can inject charges of either sign, then on shorting the electrodes a counter charge is injected, which leads to a more rapid discharge at early times but does not give rise to a current reversal (anomalous current). Materials of higher dielectric constant store more surface charge. We compare our results with previous calculations and with existing experimental work. © 1998 American Institute of Physics.
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73.25.+i Surface conductivity and carrier phenomena
77.22.Jp Dielectric breakdown and space-charge effects

The origin of Ga2O3 passivation for reconstructed GaAs(001) surfaces

Jiang Guo-Ping and Harry E. Ruda

J. Appl. Phys. 83, 5880 (1998); http://dx.doi.org/10.1063/1.367449 (5 pages) | Cited 10 times

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Ab initio molecular-orbital calculations are used to study the origin of the Ga2O3 passivation mechanism for GaAs(100) reconstructed surfaces. Two cluster models are used to simulate the main features of reconstructed and oxygen chemisorbed GaAs(100) surfaces. The simulation results show that the reduction in the density of surface states located within the bulk energy gap derives from the initial near-bridge-bonded O atoms. The calculated electronic energy spectra reveal that the surface-state energy gap lies completely outside of the bulk energy gap in distinct contrast to the case for S passivation. At the optimized geometry, each surface Ga atom (situated beneath the adsorbed O) is distorted by 0.40 Å from its ideal position, resulting in a strained surface. O atoms are almost buried in the GaAs(100) surface; each is located 0.30 and 0.25 Å above the reconstructed GaAs(100) surface, respectively. The O–Ga bond length is 1.63 Å and the Ga–O–Ga bond angle is 157.4°. Each O atom deviates from the bridge position by 0.11 and 0.19 Å from the vertical position, respectively. This causes further deposition to result in the formation of an amorphous oxide film, which provides an effective protection layer against further oxidation of the near-bridge-site oxidized GaAs surface. The calculated electronic structure and local density of states also reflect a large charge accumulation near the adsorbed O atoms.
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81.05.Ea III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
81.65.Rv Passivation
73.20.At Surface states, band structure, electron density of states
72.80.Ey III-V and II-VI semiconductors
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Investigation of the properties of plasma-enhanced chemical vapor deposited silicon nitride and its effect on silicon surface passivation

L. Cai, A. Rohatgi, S. Han, G. May, and M. Zou

J. Appl. Phys. 83, 5885 (1998); http://dx.doi.org/10.1063/1.367450 (5 pages) | Cited 13 times

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Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are used for a variety of applications in integrated circuit and solar cell industries, such as surface passivation and insulation. The objective of this article is to investigate and understand the impact of the PECVD deposition parameters on the silicon surface passivation and establish the correlation between the properties of the silicon nitride and the ensuing silicon surface recombination velocity. All the films were annealed at 350 °C for 20 min in a rapid thermal annealer after the deposition. It is shown that bonded hydrogen and positive charge in the annealed PECVD silicon nitride films have the opposite effect on the surface passivation. The surface recombination velocity decreases with the increase in the positive charge density and the decrease in the bonded hydrogen content. It is found that the deposition temperature has the most influence on achieving low surface recombination velocity. Higher deposition temperature in the range of 200–300 °C produces lower surface recombination velocity. Optimal silicon nitride deposition conditions resulted in a surface recombination velocity of 119 cm/s on 2 Ω cm p-type silicon. © 1998 American Institute of Physics.  
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72.80.Cw Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Rv Passivation
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Current–voltage characteristics of the partially Ga-terminated Si (111) surface studied by scanning tunneling microscopy

Yukihiro Kusumi, Ken Fujita, and Masakazu Ichikawa

J. Appl. Phys. 83, 5890 (1998); http://dx.doi.org/10.1063/1.367451 (6 pages) | Cited 1 time

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We investigated the current–voltage (I–V) characteristics of the Si (111) surface partially terminated by Ga atoms by using scanning tunneling microscopy. On the surface, Si (111) 7×7 and Si (111) √3×√3 Ga terraces alternated. The I–V curves of the 7×7 terraces exhibited semiconductive features, not metallic. The √3×√3 Ga terraces on the surface had narrower surface band gaps than usual √3×√3 Ga surfaces. These features could be explained by taking into account the adatom replacement between Ga and Si adatom sites. An amorphous Si layer was deposited on the surface after Sb was selectively adsorbed on the 7×7 terraces. The alternate structure was preserved after recrystallization of the Si layer. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena
72.80.Cw Elemental semiconductors
73.25.+i Surface conductivity and carrier phenomena
73.20.At Surface states, band structure, electron density of states
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Transport simulation of bulk AlxGa1−xN and the two-dimensional electron gas at the AlxGa1−xN/GaN interface

Mahesh S. Krishnan, Neil Goldsman, and Aris Christou

J. Appl. Phys. 83, 5896 (1998); http://dx.doi.org/10.1063/1.367452 (8 pages) | Cited 5 times

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In this work, a hybrid Monte Carlo simulation with the inclusion of degenerate statistics has been performed to analyze electron transport in bulk AlxGa1−xN, and the two-dimensional electron gas at the AlxGa1−xN/GaN interface. The results of the steady-state drift velocity, average electron energy, and distribution functions for bulk AlxGa1−xN are presented. A study of the change in transport properties with compositional variations has been made and presented here. Degeneracy has been found to affect electron transport in both the low- and the high-field regions. The inclusion of degeneracy caused a pronounced negative differential mobility. Simulation of the two-dimensional electron gas takes into account three subbands at the AlxGa1−xN/GaN interface. A self-consistent solution of the Schrödinger and Poisson equations at the heterointerface is obtained through a Rayleigh–Ritz method that should result in more accurate electron wave functions, and hence, more accurate scattering rates for the two-dimensional electron gas. The inclusion of degenerate statistics caused an increase in the interband occupancy in addition to an increase in the electron kinetic energy in the subbands. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Electrical deactivation of interstitial Zn in heteroepitaxial InP by hydrogen and its effect on electronic properties

S. A. Ringel and B. Chatterjee

J. Appl. Phys. 83, 5904 (1998); http://dx.doi.org/10.1063/1.367453 (9 pages) | Cited 3 times

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Hydrogen passivation of InP layers grown on lattice-mismatched substrates can achieve thermally stable deactivation of dislocation-related deep levels, making this a promising process for improving the performance of heteroepitaxial InP space solar cells. However, in addition to dislocation-related defects, interstitial Zn (Zni) defects that are characteristic of Zn-doped InP and which form deep donor states within the InP band gap, are important considerations for optimizing the electronic quality of these layers. Here, we show that hydrogen forms complexes with and deactivates Zni donor states within Zn-doped InP grown by metalorganic chemical vapor deposition. A combination of photoluminescence (PL), electrochemical capacitance–voltage dopant profiling, secondary ion mass spectroscopy and current–voltage (I–V) measurements are applied to a set of samples receiving systematic hydrogenation and annealing treatments. We find that the deactivation of Zni deep donors, as detected by monitoring the evolution of the donor–acceptor transition using PL measurements, causes an increase of ∼50% in the net acceptor concentration of heavily Zn-doped heteroepitaxial InP by elimination of the acceptor compensation effect due to active Zni donors. Analysis of I–V characteristics indicates that Zni passivation sharply reduces depletion region recombination and shunt currents within heteroepitaxial diodes, causing an increase in the diode turn-on voltage from 680 to 960 mV. Subsequent annealing above 500 °C reactivates the Zni defects, resulting in a systematic increase in doping compensation as well as a decrease in VTO toward the original, as-grown value. A study of the reactivation kinetics for the H–Zni complex reveals a greater thermal stability than that of H–Zn acceptor complexes but less than that of H-dislocation complexes in InP, with an estimated dissociation energy for the H–Zni complex of 2.3 eV. While these effects are observed for both homoepitaxial and heteroepitaxial Zn-doped layers, the effect is far more pronounced for the heteroepitaxial layers due to the relatively high Zni concentration in the latter. © 1998 American Institute of Physics.
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81.65.Rv Passivation
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Ea III-V semiconductors
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Fk Electrochemical methods
84.60.Jt Photoelectric conversion
78.55.Cr III-V semiconductors
73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.60.Dv Thermal stability; thermal effects

Growth and small polaron properties of epitaxial La1−xCaxMnO3 thin films

D. C. Worledge, L. Miéville, and T. H. Geballe

J. Appl. Phys. 83, 5913 (1998); http://dx.doi.org/10.1063/1.367454 (4 pages) | Cited 12 times

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We report on the epitaxial growth and properties of La1−xCaxMnO3 thin films deposited by pulsed laser ablation. We grew and characterized 11 thin films covering the entire doping range, from x = 0 to x = 1. A presence of oxygen during postdeposition annealing is shown to be required in order to reduce the resistivity of the samples and to obtain reproducible samples. The lattice constant and phonon frequency that appear in the Emin–Holstein, [D. Emin and T. Holstein, Ann. Phys. 53, 439 (1969).] adiabatic small polaron conductivity formula are reported. Resistivity data from 20 to 300 K are also reported. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.38.-k Polarons and electron-phonon interactions
73.61.Ng Insulators

Experimental study of the effective secondary emission coefficient for rare gases and copper electrodes

G. Auday, Ph. Guillot, J. Galy, and H. Brunet

J. Appl. Phys. 83, 5917 (1998); http://dx.doi.org/10.1063/1.367455 (5 pages) | Cited 36 times

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Measurements are made for variations of the effective secondary emission coefficient γ with reduced field E/p. Plane-parallel copper electrodes (5 cm diameter) are sustained with a dc voltage (0<V<1 kV) and can be separated by a variable distance (2 mm<d<1 cm). Current–voltage characteristics, Paschen curves, and γ(E/p) variations are shown for various rare gases (neon, argon, krypton, and xenon). γ(E/p) values are deduced from Paschen curves and published α/p(E/p) variations by using the self-sustain condition. Comparisons are made with various experimental or calculated results taken from the literature. © 1998 American Institute of Physics.
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79.20.Hx Electron impact: secondary emission

Theory of magnetoelastic dissipation due to domain wall width oscillation

Y. Liu and P. Grütter

J. Appl. Phys. 83, 5922 (1998); http://dx.doi.org/10.1063/1.367456 (5 pages) | Cited 8 times

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This article presents a general treatment of magnetic dissipation due to domain wall width oscillation via magnetostriction in magnetic samples. The domain wall width is modeled as a harmonic oscillator. The parameters governing this oscillator (effective mass, stiffness, damping coefficient and driving force) are derived and expressed in terms of intrinsic magnetic parameters of magnetic materials. The magnetostriction induced damping of wall width oscillations is frictional in nature. An external ac magnetic field serves as a driving force of the oscillator. It is found that the response to the driving force depends very much on the micromagnetic structures of the magnetic domain wall. Different micromagnetic structures lead to different magnetic dissipation for a given external field. Besides giving a quantitative microscopic explanation to magnetic dissipation data measured by magnetic dissipation force microscopy, this theory predicts two new phenomena: one is that there is a minimum driving force for the wall width to oscillate and the other is a new resonance phenomenon, domain wall width resonance. © 1998 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ch Domain walls and domain structure

Magnetoresistance, Hall effect, and thermoelectric power in spin valves

H. Sato, S. Miya, Y. Kobayashi, Y. Aoki, H. Yamamoto, and M. Nakada

J. Appl. Phys. 83, 5927 (1998); http://dx.doi.org/10.1063/1.367457 (6 pages) | Cited 5 times

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Comparison of the magnetoresistance (MR) on two groups of spin-valve multilayers, NiO/NiFe/Cu/NiFe/Cu/NiO and NiO/NiFe/Cu/NiFe/Cu, has been made in order to investigate the possibility of the enhanced specular scattering at NiO/metal interface. No clear difference in MR between the two systems has been found, suggesting that the enhancement of specular scattering at interfaces is not the origin of the large MR. For the field direction almost perpendicular to the plane, we found a sensitive angular dependence of MR along with a large unidirectional anisotropy. To sort out any specific characteristics of the spin-valve system compared to the multilayers, thermoelectric power and Hall effect have been investigated for the first time. © 1998 American Institute of Physics.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.15.Jf Thermoelectric and thermomagnetic effects
75.47.De Giant magnetoresistance
73.61.At Metal and metallic alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys

Generalized inclusion model for the coercivity of soft magnetic materials

L. Lopez Diaz and E. Della Torre

J. Appl. Phys. 83, 5933 (1998); http://dx.doi.org/10.1063/1.367458 (9 pages) | Cited 9 times

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The principal causes of coercivity in soft magnetic materials are the imperfections in the structure of the crystal, such as inclusion and grain boundaries, that pin domain walls. The models that have been proposed so far in order to explain this effect are only valid for a specific range of material parameters. In this paper, we present a two-dimensional micromagnetic model for Barkhausen coercivity due to inclusions that is valid for all physically realizable material parameters. The details of the interaction between Bloch walls and nonmagnetic inclusions are presented for some interesting special cases. One of the results the model predicts is that walls are stable when they are centered on the inclusion. Furthermore, much higher values of the coercivity are obtained than those predicted by previous models. © 1998 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Qq Microscopic defects (voids, inclusions, etc.)
75.60.Ch Domain walls and domain structure
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