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1 Sep 1996

Volume 80, Issue 5, pp. 2555-3134

Page 2 of 4 Pages Previous Page Next Page | Jump to Page

Solid solubility and diffusion of boron in single‐crystalline cobalt disilicide

C. Zaring, A. Pisch, J. Cardenas, P. Gas, and B. G. Svensson

J. Appl. Phys. 80, 2742 (1996); http://dx.doi.org/10.1063/1.363202 (7 pages) | Cited 8 times

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The temperature dependence of the solid solubility [CsCoSi2(B)] and the lattice diffusion coefficient [DCoSi2(B)] of boron in single‐crystalline cobalt disilicide (CoSi2) has been investigated between 450 and 1000 °C. Both CsMCoSi2(B) and DCoSi2(B) are found to be considerably higher than the corresponding quantities in silicon. Using a thermodynamical interpretation, the experimental data show that boron‐doped CoSi2 can be described as a regular solution in the dilute limit with an enthalpy of solution of ∼−0.4 eV. The experimental data and theoretical estimates of the excess enthalpy of solution indicate a weak interaction of boron with the silicon and cobalt atoms in CoSi2 suggesting that the boron atoms occupy sites in the CoSi2 lattice with a small contribution to the Gibbs energy of the solution phase. The diffusion data yield a high mobility of the boron atoms with an activation energy of ∼2.0 eV for the lattice diffusion coefficient which is ∼1.0 eV lower than that reported for the self‐diffusion of Si(Ge) and Co in CoSi2. Boron is a small atom which can occupy interstitial sites in the relatively opened CaF2 structure of CoSi2, and it is argued that the diffusion of boron may occur via a mixed process where interstitial/substitutional interchange takes place, including trapping and detrapping of the boron atoms. © 1996 American Institute of Physics.
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64.75.-g Phase equilibria
66.30.J- Diffusion of impurities

Electronic effects of ion mobility in semiconductors: Mixed electronic–ionic behavior and device creation in Si:Li

Leonid Chernyak, Vera Lyakhovitskaya, Shachar Richter, Abram Jakubowicz, Yishay Manassen, Sidney R. Cohen, and David Cahen

J. Appl. Phys. 80, 2749 (1996); http://dx.doi.org/10.1063/1.363132 (14 pages) | Cited 6 times

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Micrometer‐sized homojunction structures can be formed by applying strong electric pulses, at ambient temperatures, to Li‐doped, floating zone n‐Si. Two such junctions, arranged back to back, act as a transistor, as evidenced by electron‐beam‐induced current and current–voltage measurements. The structures are created during a time ranging from ∼100 ms to a few seconds, depending on the size of the structure. The phenomenon is similar to what was observed earlier in CuInSe2 and was explained there by thermally assisted electromigration of Cu. In the case of Si doped with Li we can use secondary‐ion‐mass spectrometry to detect the redistribution of Li after electric‐field application. Such a redistribution is indeed found and corresponds to an n+‐p‐n structure with the p region extending at least ∼20 μm into the bulk of Si. Structures created in Si doped with Li in this way are stable for at least 13 months after their creation. We ascribe this to the large difference between Li diffusivity at the local temperature that is reached during structure formation (∼400 °C; 10−8 cm2/s) and at room temperature (∼10−15 cm2/s). © 1996 American Institute of Physics.
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66.30.Qa Electromigration
72.60.+g Mixed conductivity and conductivity transitions
85.30.Pq Bipolar transistors

Stress relaxation in highly strained InAs/GaAs structures as studied by finite element analysis and transmission electron microscopy

T. Benabbas, P. François, Y. Androussi, and A. Lefebvre

J. Appl. Phys. 80, 2763 (1996); http://dx.doi.org/10.1063/1.363193 (5 pages) | Cited 69 times

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Finite element (FE) analysis and transmission electron microscopy (TEM) observations have been used to model stress relaxation in InAs quantum dots deposited on (001) GaAs. TEM observations show that these islands are coherently strained and the corresponding strain contrast is simulated using the dynamical electron diffraction contrast theory. The dot strain fields used for the TEM contrast simulations are deduced from FE calculations. These calculations show that elastic stress relaxation mainly occurs at the crest of the island and that the underlying substrate is under tension. That experimental TEM images and simulated images should match shows that the FE method of determination of the dot strain fields is valid (even in the case of microscopic objects), and that the shape of islands can be specified. © 1996 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Formation of buried TiN in glass by ion implantation to reduce solar load

Gary S. Was, Victor Rotberg, Dennis Platts, John Bomback, and Robert Benoit

J. Appl. Phys. 80, 2768 (1996); http://dx.doi.org/10.1063/1.363194 (6 pages) | Cited 9 times

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Ti and N were implanted into soda lime glass to doses up to 4.5×1017 cm−2 to reduce solar load and infrared transmission. Analysis of the Ti+N implant distributions by Rutherford backscattering spectrometry and x‐ray photoelectron spectroscopy (XPS) revealed profiles which closely followed each other as designed by the selection of implant energies. XPS, x‐ray diffraction, and selected area electron diffraction in transmission electron microscopy also confirmed the existence of a crystalline B1‐type, cubic TiN layer, 140 nm wide, at doses greater than 9×1016 cm−2. Optical measurements showed that the fraction of infrared radiation reflected was increased by almost a factor of 4 compared to an increase of 1.8 in the visible region. The percentage of the total solar energy rejected reached 80% at the highest dose, indicating that the buried TiN layer is highly effective in reducing solar energy transmission. © 1996 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
42.70.Ce Glasses, quartz
42.88.+h Environmental and radiation effects on optical elements, devices, and systems

Spalling of Cu6Sn5 spheroids in the soldering reaction of eutectic SnPb on Cr/Cu/Au thin films

Ann A. Liu, H. K. Kim, K. N. Tu, and Paul A. Totta

J. Appl. Phys. 80, 2774 (1996); http://dx.doi.org/10.1063/1.363728 (7 pages) | Cited 71 times

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The growth and morphology of intermetallic compounds between the solder and substrate play an important role in the solderability and reliability of electronic solder joints. Solder on thin films, as in chip joint, acts as an electrical and mechanical/physical interconnection between the chip and the substrate. We have studied the interfacial reactions between eutectic SnPb (63Sn37Pb, wt%) and Cr/Cu/Au thin films. Our results found here have been compared to the solder reaction on bulk Cu. The eutectic solder has 7° of wetting angle on Cr/Cu/Au thin films rather than 11° on Cu substrate. Sideband around the solder cap was found in both the thin film case and the Cu case. Spalling of Cu6Sn5 compound grains occurred in the thin‐film case when the Cu film was consumed but not in the case of bulk Cu. We observed a shape change from hemispherical ‘‘scallops’’ to spheroids before spalling took place. The shape change is assisted by ripening a reaction among the scallops. We have calculated a critical size of the scallop, depending on the Cu film thickness, when the shape change or spalling starts. © 1996 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
68.08.Bc Wetting
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.20.Vj Joining; welding

Stability of ion‐implanted layers on MgO under ultrasonic cavitation

L. J. Romana, J. Rankin, J. R. Brewster, L. A. Boatner, and A. M. Williams

J. Appl. Phys. 80, 2781 (1996); http://dx.doi.org/10.1063/1.363195 (7 pages) | Cited 1 time

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The effects of ion implantation and ultrasonic cavitation on the near‐surface region of MgO single crystals were investigated. For 150 keV, room‐temperature implantations of Ar+ or K+ at 5×1016–1017 ions cm−2 into a (100)‐oriented surface of MgO, a dilatometric swelling of the implanted layer is observed perpendicular to the implanted surface. When these strained surface layers are then subjected to an ultrasonic (∼20 kHz) cavitation treatment, uniform layers (∼100–200 nm) can be removed from the MgO surface in a controlled manner. The thickness of the removed layer is directly related to the duration of the ultrasonic irradiation, but does not exceed the depth of the implanted species. When MgO implanted with Ar+ or Kr+ at fluences of 5×1016–1017 ions cm−2 is subsequently irradiated with 2 MeV He+ ions at 1016–1017 ions cm−2, the region exposed to the He+ beam is effectively ‘‘stabilized’’ and is not removed by the ultrasonic treatment. K+ or Ar+ implantations at <5×1016 ions cm−2 produced no swelling of the layer, and subsequent ultrasonic irradiation with an energy flux of ∼120 W cm−2 did not remove the crystal surface as determined by profilometry. For MgO implanted with ≳2×1017 ions cm−2, the implanted layer is highly strained and detaches from the underlying crystal without exposure to ultrasonic‐cavitation effects. These findings are discussed in terms of the stressed states of the implanted layers, and their potential applications to the mechanical ‘‘etching’’ of ceramics are considered.
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68.35.Gy Mechanical properties; surface strains
61.72.up Other materials
62.80.+f Ultrasonic relaxation

Fitting of x‐ray or neutron specular reflectivity of multilayers by Fourier analysis

Ming Li, M. O. Möller, and G. Landwehr

J. Appl. Phys. 80, 2788 (1996); http://dx.doi.org/10.1063/1.363196 (3 pages) | Cited 9 times

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The dependence of x‐ray or neutron specular reflectance on the scattering density has been linearized by modifying the Born approximation. This makes it possible to analyze the reflectivity curves by the Fourier transform method by using the box refinement technique. Thus, the phases of the scattered waves are iteratively obtained, by which the scattering density profile in layered systems can be directly evaluated. The validity of these modifications is demonstrated by some numerical examples. The box refinement technique requires fewer constraints to obtain the physically realistic scattering density than the least‐squares‐fitting method does. © 1996 American Institute of Physics.
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61.05.cm X-ray reflectometry (surfaces, interfaces, films)
61.05.fj Neutron reflectometry
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness

Microstructure of diamond and β‐SiC interlayer studied by synchrotron x‐ray scattering

J. H. Je and D. Y. Noh

J. Appl. Phys. 80, 2791 (1996); http://dx.doi.org/10.1063/1.363197 (8 pages) | Cited 7 times

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The microstructure of the diamond and the β‐SiC interlayer grown on Si substrates was studied in synchrotron x‐ray scattering experiments. In the process of growing diamond using microwave plasma chemical vapor deposition, a β‐SiC interlayer was always formed epitaxially regardless to the orientation and the pretreatment of substrates. The crystalline axes of the β‐SiC interlayer were parallel to the substrate crystalline axes. The pretreatment of the silicon substrates greatly enhanced the growth rate of the β‐SiC. Meanwhile, the diamond particles were preferentially grown along both the 〈111〉 and the 〈001〉 directions on all the pretreated substrates. The diamond particles that were grown with the preferred growth direction matching to the substrate normal crystalline axis direction exhibited partial epitaxy, while others were grown nonepitaxially. The substrate pretreatment also enhanced the growth of diamond particles significantly. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.05.cf X-ray scattering (including small-angle scattering)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Effect of SiO2 buffer layers on the structure of SrTiO3 films grown on silicon by pulsed laser deposition

P. Tejedor, V. M. Fuenzalida, and F. Briones

J. Appl. Phys. 80, 2799 (1996); http://dx.doi.org/10.1063/1.363198 (6 pages) | Cited 6 times

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Thin films of SrTiO3 were grown by pulsed laser deposition on Si and SiO2/Si at 35 and 650 °C in a 50 mTorr oxygen discharge (300 V). The effect of introducing a SiO2 buffer layer between the Si substrate and the complex oxide on the crystallinity and microstructure of the SrTiO3 films was investigated at both deposition temperatures. All films grown at 35 °C were amorphous. Surface morphology examination by scanning electron microscopy (SEM) showed that these films were continuous and homogeneous when grown on Si, but were porous and had low‐density noninterconnecting lines when grown on SiO2/Si. Films prepared at 650 °C were polycrystalline and their x‐ray‐diffraction patterns exhibited peaks corresponding to the (001), (110), (111), and (002) reflections of the SrTiO3 cubic phase (a=3.904 Å). The films deposited on SiO2/Si were found to grow with a high degree of preferred orientation along the (110) direction. SEM studies on the surface morphology of the films grown at high temperature showed the presence of a ‘‘rosette’’ structure. The mean size of the rosettes was ∼80 nm in 40‐nm‐thick films grown on Si and ∼100 nm in films of similar thickness grown on SiO2/Si. Additional atomic force microscopy studies on the topography of these samples indicated that the rosettes were constituted by ∼35‐nm‐diam grains. Typical peak‐to‐valley surface roughness of these films was 0.5–2 nm. © 1996 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Improved linear prediction for deep level transient spectroscopy analysis

Edward A. Ingham, James D. Scofield, and Meir Pachter

J. Appl. Phys. 80, 2805 (1996); http://dx.doi.org/10.1063/1.363133 (10 pages)

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A novel linear prediction based parameter estimation algorithm is developed for analyzing deep level transient spectroscopy (DLTS) signals. The algorithm performs significantly better than a current linear prediction based algorithm used in DLTS because it accurately accounts for the effects of noise and any underlying baseline constant. The algorithm is developed for any digitized isothermal capacitance transient. It does not rely on overmodeling or require baseline nulling hardware. The superior performance of the algorithm is verified on synthesized, as well as challenging actual DLTS signals. It is shown to consistently extend the linear regions and resolve closely spaced activation energies on Arrhenius plots.
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71.55.-i Impurity and defect levels
85.30.De Semiconductor-device characterization, design, and modeling

Electron interaction with confined acoustic phonons in cylindrical quantum wires via deformation potential

SeGi Yu, K. W. Kim, Michael A. Stroscio, G. J. Iafrate, and Arthur Ballato

J. Appl. Phys. 80, 2815 (1996); http://dx.doi.org/10.1063/1.363199 (8 pages) | Cited 5 times

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The effects of phonon confinement on electron–acoustic‐phonon scattering is studied in cylindrical semiconductor quantum wires. In the macroscopic elastic continuum model, the confined‐phonon dispersion relations are obtained for several crystallographic directions with the two cardinal boundary conditions: free‐surface and clamped‐surface boundary conditions. The scattering rates due to the deformation potential interaction are obtained for these confined phonons and are compared with those of bulk‐like phonons for a number of quantum wire materials. The results show that the inclusion of acoustic phonon confinement effects may be crucial for calculating accurate low‐energy electron scattering rates in nanostructures. It is also demonstrated that the scattering rates may be significantly influenced by the direction of phonon propagation, especially for low‐energy electrons. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates: the directions characterized by small Poisson ratios exhibit large scattering rates. © 1996 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Bk General theory, scattering mechanisms
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Structural, electronic, and luminescence investigation of strain‐relaxation induced electrical conductivity type conversion in GeSi/Si heterostructures

P. N. Grillot, S. A. Ringel, J. Michel, and E. A. Fitzgerald

J. Appl. Phys. 80, 2823 (1996); http://dx.doi.org/10.1063/1.363200 (10 pages) | Cited 14 times

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Strain‐relaxed, compositionally graded Ge0.3Si0.7/Si heterostructures grown by ultrahigh vacuum chemical vapor deposition at 650 °C are shown to display a consistent change from p‐type to n‐type conductivity as a function of rapid thermal annealing (RTA) temperature in the range 700–850 °C. Cross‐sectional transmission electron microscopy, spreading resistance, and electron beam induced current (EBIC) studies eliminate the dislocations themselves as a possible source of this type conversion, by demonstrating that the spatially invariant hole concentration of 2×1014 cm−3 is not correlated to the dislocation density, which decreases from ∼108 cm−2 in the graded region to 7×105 cm−2 in the 30% Ge cap. To identify the source of type conversion, a systematic investigation was performed on 650 °C as‐grown and annealed samples with deep‐level transient spectroscopy (DLTS), photoluminescence (PL) and capacitance–temperature (C–T) measurements. DLTS measurements on as‐grown samples reveal a complex spectrum of deep and shallow hole traps, while C–T studies reveal a prominent temperature dependence of the zero bias capacitance, indicating that the p‐type background conductivity is associated with a high degree of compensation. Post‐growth RTA at T≥800 °C eliminates this compensation, and yields background n‐type films, consistent with the background n‐type conductivity that is always observed in graded films grown at T≳800 °C in the same reactor. This change in conductivity type is accompanied by a strong increase in EBIC signal strength and a significant simplification of DLTS and PL spectra. These results are discussed in terms of dislocation interaction within the graded layers which generates nonequilibrium concentrations of intrinsic point defects that form extended complexes at growth temperatures ≤800 °C. These complexes are associated with thermally unstable acceptor‐like defect states in the energy range H(0.05)–H(0.30) that convert low growth temperature, relaxed, graded GeSi/Si films from background n type to background p type. © 1996 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.80.Cw Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Ap Elemental semiconductors

Structure and electrical properties of CdNiTe nanostructured thin films

O. Alvarez‐Fregoso, J. G. Mendoza‐Alvarez, O. Zelaya‐Angel, and F. Morales

J. Appl. Phys. 80, 2833 (1996); http://dx.doi.org/10.1063/1.363201 (5 pages) | Cited 3 times

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CdNiTe nanostructured thin films were prepared by radio frequency sputtering from a target of CdTe and nickel compressed powders. The structural and electrical film properties were studied as a function of the atomic nickel concentration in the films (x=0.05, 0.10, and 0.15). X‐ray diffraction patterns showed a cubic CdTe parent structure with a (111) preferential orientation. The microcrystalline grain size in the films showed a systematic decrease with the increase of Ni content, starting with grain sizes of around 35 nm for x=0.05, down to an average of 26 nm for x=0.15. From scanning electron microscopy micrographs, a fine granular morphology with a random distribution of grain sizes in the films was observed. The film electrical resistivity was measured as a function of the temperature in the range T: 26–473 K. The temperature dependence of the dark resistivity over this wide temperature range showed a clear deviation from a simple thermally activated carrier transport mechanism. © 1996 American Institute of Physics.
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73.63.-b Electronic transport in nanoscale materials and structures
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

High level injection phenomena in P–N junctions

J. C. Manifacier, R. Ardebili, and C. Popescu

J. Appl. Phys. 80, 2838 (1996); http://dx.doi.org/10.1063/1.363134 (9 pages) | Cited 2 times

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To model high injection phenomena in P–N junction devices it is usually necessary to use numerical analysis. This is because the standard procedure of dividing the structure into neutral zones and depletion layer (regional approximation) fails. In a recent paper, Yue et al. [J. Appl. Phys. 77, 1611 (1995)] proposed an extension of the Shockley theory, retaining the form of the conventional diffusion current‐only model for the conduction mechanism. Their solution was based on the resolution of the ambipolar transport equation in the base. It is shown here by a numerical simulation of the complete structure, within the framework of the drift‐diffusion model, that both the exponential current dependence: Jα exp(eVa/2kT) as well as the Yue et al. approximation are valid only in the limiting case of a strongly extrinsic short base diode. © 1996 American Institute of Physics.
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72.20.Dp General theory, scattering mechanisms
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.80.Cw Elemental semiconductors

Carrier compensation and scattering mechanisms in p‐GaSb

P. S. Dutta, V. Prasad, H. L. Bhat, and Vikram Kumar

J. Appl. Phys. 80, 2847 (1996); http://dx.doi.org/10.1063/1.363135 (7 pages) | Cited 10 times

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The hole transport properties of gallium antimonide with various degrees of tellurium compensation have been investigated in the temperature range of 4.2–300 K. For the undoped GaSb, the p‐type conductivity arises from a doubly ionizable native defect VGa GaSb. In the Te compensated samples, apart from the Te‐donor level and the VGaGaSb center, an acceptor level resulting from complexation of VGa GaSb with TeSb has been found. This acceptor level lies ∼70 meV above the valence band edge. The concentration of this center depends on the melt composition and the level of Te present in the melt during growth of crystals. Most interestingly, at very low level of Te concentration, an additional triple native acceptor (VGa GaSb VGa) has also been observed. With the increase in Te concentration, the mobility decreases and a shift in the mobility peak to higher temperature is observed. The low‐temperature mobility is limited by ionized impurity scattering. At higher temperatures, the scattering mechanisms depend on Te concentration in the sample. In this regime, significant contributions from acoustic, nonpolar optical, and polar optical phonon scattering are observed for samples with low levels of Te. In contrast, the impurity scattering dominates even at room temperature for highly compensated crystals. © 1996 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Ey III-V and II-VI semiconductors

Thermoelectric amplification of phonons in bulk semiconductors under a strong magnetic field

C. Rodrigues, A. L. A. Fonseca, and O. A. C. Nunes

J. Appl. Phys. 80, 2854 (1996); http://dx.doi.org/10.1063/1.363136 (6 pages) | Cited 1 time

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We consider the problem of phonon instability in an electron‐phonon system of a semiconductor in a temperature field upon variation of a strong (quantizing) static magnetic field. It is found that the phonons may become unstable when certain values for the temperature gradient‐drift velocity and the magnetic field are exceeded. However, even after the thresholds are exceeded, it is predicted that there exist alternate bands of the magnetic field, in which the phonons are unstable in one band, stable in the next band, unstable again in the following band, etc. These alternate bands have their origin in the discreteness of the Landau levels of the electrons. An application is made for a GaAs sample. © 1996 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
63.20.K- Phonon interactions

Deep levels in uniformly Si doped GaAs/AlxGa1−xAs quantum wells and superlattices

Y. B. Jia, Z. Y. Han, H. G. Grimmeiss, and L. Dobaczewski

J. Appl. Phys. 80, 2860 (1996); http://dx.doi.org/10.1063/1.363137 (6 pages) | Cited 3 times

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Uniformly Si doped GaAs/Al0.33Ga0.67As multilayer structures have been studied by deep level transient spectroscopy (DLTS) and photocapacitance measurements. DLTS spectra showed five peaks which are related to defects in the GaAs layers. The concentration of these defects decreased with increasing layer thickness. An additional peak, which has been observed with forward bias filling pulses, is suggested to be related to defects near the surface, most probably due to defect accumulation in multilayers. Their emission and capture properties as well as photoionization cross sections have been studied. Evidence is provided that the emission and filling processes of these deep levels are modified due to the energy quantization in the conduction band and the carrier transport through the quantum structures. No DX center related DLTS peaks or other features like persistent photoconductivity effects have been observed in any of our samples. © 1996 American Institute of Physics.
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73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors

Carrier spillover at 300, 195, and 77 K in InGaAs and GaAs single quantum wells

Andrew P. Ongstad, Michael L. Tilton, Erik J. Bochove, and Gregory C. Dente

J. Appl. Phys. 80, 2866 (1996); http://dx.doi.org/10.1063/1.363138 (7 pages) | Cited 6 times

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The carrier recombination rates in GaAs and strained InGaAs–GaAs single‐quantum‐well lasers of varying well width and potential depth, respectively, have been measured at 300, 195, and 77 K. For the InGaAs quantum wells (QWs), the carrier lifetime saturates at high inversion, with both the Shockley–Read (SR) lifetime and the saturation lifetime showing substantial reductions with decreasing temperature. The large reduction in the SR lifetime may be attributed to the increased effectiveness of acceptor ions as trap sites, due to the reduced carrier momentum at lower temperature. In a similar vein, the saturation lifetime is also reduced, due to the enhanced carrier confinement in the QW, brought about by the decrease in the carrier thermalization. For the GaAs QWs at 300 K, the saturation lifetime decreases as the well width is increased. The recombination rate law of bulk material is inadequate to predict the recombination rates in these QWs. Consequently, a local recombination model has been developed which accurately predicts the observed lifetime saturation behavior as a function of well width, potential depth, and temperature. Further, T0 of 95 and 162 K are calculated for the shallow and deep QW lasers, respectively. This calculation suggests that it is the temperature dependence of the differential gain that is the dominant factor in setting the temperature sensitivity of the InGaAs QW lasers.
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78.66.Fd III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
42.55.Px Semiconductor lasers; laser diodes

Analysis of thin CdS layers on InP for improved metal–insulator–semiconductor devices

Helen M. Dauplaise, Kenneth Vaccaro, Andrew Davis, George O. Ramseyer, and Joseph P. Lorenzo

J. Appl. Phys. 80, 2873 (1996); http://dx.doi.org/10.1063/1.363139 (10 pages) | Cited 10 times

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Cadmium sulfide (CdS) layers were deposited from an aqueous solution of thiourea, cadmium sulfate, and ammonia on (100) n‐InP at 60–95 °C. X‐ray photoelectron spectroscopy showed that the deposition process effectively removes native oxides on InP and forms a protective layer for subsequent dielectric deposition. Surface analysis also showed that the InP surface is not P deficient following oxide deposition on CdS‐treated InP. Capacitance–voltage and conductance–voltage measurements of metal–insulator–semiconductor (MIS) capacitors were used to compare samples with and without CdS films between InP and a deposited insulator. Capacitance–voltage response of CdS‐treated MIS structures showed well‐defined regions of accumulation, depletion, and inversion. The interface‐state density at midgap was reduced from 5×1011 to 6×1010 eV−1 cm−2 with CdS treatment. Depletion‐mode MIS field‐effect transistors made using this new passivation technique exhibited superior device performance to that of untreated samples.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.At Surface states, band structure, electron density of states
85.30.De Semiconductor-device characterization, design, and modeling

Systematic investigation of the effects of organic film structure on light emitting diode performance

M. D. Joswick, I. H. Campbell, N. N. Barashkov, and J. P. Ferraris

J. Appl. Phys. 80, 2883 (1996); http://dx.doi.org/10.1063/1.363140 (8 pages) | Cited 32 times

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We present a systematic investigation of the effects of organic film structure on light emitting diode (LED) performance. Metal/organic film/metal LEDs were fabricated using a five ring, poly(phenylene vinylene) related oligomer as the active layer. The structure of the vacuum evaporated oligomer films was varied from amorphous to polycrystalline by changing the substrate temperature during deposition. The intrinsic properties of the oligomer films and the LED performance were measured. The measured intrinsic film properties include: optical absorption, photoluminescence (PL) spectra, PL lifetime, PL efficiency, and effective carrier mobility. The measured device characteristics include current–voltage, capacitance–voltage, electroluminescence (EL) efficiency, and the contact metal/organic film Schottky barrier heights. The optical absorption and PL properties of the films are weakly dependent on film structure but the effective carrier mobility decreases with increasing crystallinity. The EL quantum efficiency decreases by more than one order of magnitude, the drive voltage at a fixed current increases, and the electron Schottky barrier height increases as the crystallinity of the film is increased. The diode current–voltage characteristic is determined by the dominant hole current and the electroluminescence efficiency is controlled by the contact limited electron injection. These results demonstrate significant effects of organic film structure on the performance of organic LEDs. © 1996 American Institute of Physics.
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61.41.+e Polymers, elastomers, and plastics
85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds

Thermal reactions of Pd/AlxGa1−xAs contacts

H. F. Chuang, C. P. Lee, J. S. Tsang, and J. C. Fan

J. Appl. Phys. 80, 2891 (1996); http://dx.doi.org/10.1063/1.363141 (5 pages) | Cited 1 time

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Pd/AlxGa1−xAs Schottky contacts and their thermal reactions are studied by capacitance–voltage measurements, current–voltage measurements, and x‐ray diffraction. The thickness of AlxGa1−xAs consumed by the Pd/AlxGa1−xAs reaction during annealing was calculated. For annealing temperatures below 300 °C the Schottky characteristics of the diodes were good but the electrical junction moves into AlxGa1−xAs after annealing. The amount of junction movement was calculated directly from our measurements. The diffusion coefficients of Pd in AlxGa1−xAs and the activation energy were estimated. The activation energy was found to be larger for higher Al concentration. PdAl, PdAs2, PdGa5, and Pd5Ga2 were detected in the compounds formed by the Pd/AlxGa1−xAs reaction after annealing. © 1996 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
68.60.Dv Thermal stability; thermal effects
68.35.Fx Diffusion; interface formation

Bonding structure and characteristics of defects of near‐stoichiometric silicon nitride films

S. Hasegawa, M. Ikeda, T. Inokuma, and Y. Kurata

J. Appl. Phys. 80, 2896 (1996); http://dx.doi.org/10.1063/1.363142 (8 pages) | Cited 6 times

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Amorphous SiNx:H films having nitrogen content x greater than 1.3 were deposited at 300 °C by varying the ammonia‐to‐monosilane flow‐rate ratio RN, using plasma‐enhanced chemical‐ vapor‐deposition. The characteristics of defects in the films subjected to UV illumination and anneal treatments were investigated by electron‐spin‐resonance (ESR) measurements. The paramagnetic Si dangling bonds (DBs) with three N atom neighbors, called the K0 center, were observed for an as‐deposited film with RN of 5, and the density was favorably enhanced by exposing the film to UV light or by the UV illumination subsequent to its annealing. The K0 density decreased as the film was annealed at 550 °C after the UV illumination. The mechanisms of creation and disappearance of the K0 centers by the illumination and the annealing, respectively, were interpreted in terms of the potential fluctuation model. The K0 density in as‐deposited films decreased with RN, and a new three‐line spectrum was observed as RN exceeds 7. Origins of this new spectrum are discussed. The ESR spectra due to N DBs were observed for only the films subjected to the anneal/illumination sequence, and the densities of both N DBs and K0 centers decreased with increasing the annealing time before the illumination. © 1996 American Institute of Physics.
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61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
76.30.Mi Color centers and other defects

A simple transport model for submicron semiconductor device analysis

J. O. Bark and G. Gildenblat

J. Appl. Phys. 80, 2904 (1996); http://dx.doi.org/10.1063/1.363143 (4 pages)

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A modified hydrodynamic model for the analysis of submicron semiconductor devices is derived from the first four moments of a Boltzmann transport equation without invoking any phenomenological relations. Instead, the balance equations are truncated using a suitable ansatz for the electron distribution function in the fourth moment equation. Both conventional and modified hydrodynamic models are applied to an n+n−n+ ballistic diode, and the results are compared. The new approach successfully suppresses spurious velocity overshoot without increasing the complexity of the model. Finally, the simulation of a two‐dimensional submicron metal‐oxide‐semiconductor field‐effect transistor by the modified hydrodynamic model is presented. © 1996 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
85.30.Tv Field effect devices
73.50.Bk General theory, scattering mechanisms

Excitonic properties in Zn1−xCdxSe/ZnSe multi‐quantum well structures by one‐ and two‐photon spectroscopy

M. C. Netti, M. Lepore, A. Adinolfi, R. Tommasi, I. M. Catalano, L. Vanzetti, L. Sorba, and A. Franciosi

J. Appl. Phys. 80, 2908 (1996); http://dx.doi.org/10.1063/1.363144 (6 pages) | Cited 6 times

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A detailed investigation of excitonic states by means of one‐ and two‐photon absorption photoluminescence excitation spectroscopy in Zn1−xCdxSe/ZnSe multi‐quantum wells is reported. Ground state and excited heavy‐ and light‐hole excitons associated with the n=1,2 subbands have been selectively probed exploiting the different selection rules governing one‐ and two‐photon absorption processes. Experimental exciton transition energies are found to be in good agreement with theoretical predictions when strain and confinement effects are included. The comparison between experiments and theory allowed us to single out a well defined set of band parameters and to gauge the band‐offsets in these heterostructures. Furthermore, the absorption band edge clearly evident in the two‐photon absorption photoluminescence excitation spectra allowed us to directly measure excitonic binding energies with good accuracy. © 1996 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors

Thin film of lithium niobium oxynitride as ionic conductor

Le Quang Nguyen and Vo‐Van Truong

J. Appl. Phys. 80, 2914 (1996); http://dx.doi.org/10.1063/1.363145 (4 pages) | Cited 2 times

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A novel glassy ionic conductor, lithium niobium oxynitride, was prepared in form of thin films and characterized. Thin‐film deposition was carried out by rf magnetron sputtering of LiNbO3 target in nitrogen‐containing atmosphere. These films exhibit ionic conductivity of two orders higher than that of LiNbO3 films, the room‐temperature conductivity being about 5×10−7 S cm−1. Film structure is highly cross linked, leading to activation energy as low as 0.5 eV. Film transmittance is higher than 85% in both the visible and solar ranges, making them also suitable for use in electrochromic devices. © 1996 American Institute of Physics.
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73.61.Jc Amorphous semiconductors; glasses
81.15.Cd Deposition by sputtering
78.66.Jg Amorphous semiconductors; glasses
42.70.Ce Glasses, quartz
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