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  • 1
    Electronic Resource
    Electronic Resource
    Physical mechanisms of photoluminescence of chlorine-doped ZnSe epilayers grown by molecular beam epitaxy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2314-2320 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reported here are some temperature-dependent and excitation-dependent photoluminescence (PL) results from chlorine-doped ZnSe layers grown by molecular beam epitaxy. The PL spectrum is characterized by an overwhelming exciton recombination emission at 2.797 eV (10 K) near the band edge, and no other PL features are found. This overwhelming neutral donor-bound exciton (Cl0X) emission line at 2.797 eV (10 K) with a full width at half maximum (FWHM) of ∼13 meV reveals the high crystalline quality of the samples. The quick quenching of this exciton line above 200 K is due to the presence of a nonradiative center with a thermal activation energy of ∼90 meV. The decrease of the Cl0X line over the temperature range from 10 to 200 K is due to the thermal activation of Cl0X bound excitons to free excitons with an activation energy of ∼9.0 meV. The change of the emission nature occurs at about ∼200 K from Cl0X bound exciton recombination to free exciton recombination; accordingly, a kink appears on the temperature-dependent FWHM curve at ∼190 K. The broadening behavior of the Cl0X line over the temperature range 10–200 K can be understood within the theoretical framework of the phonon scattering model, while the impurity scattering mechanisms are responsible for the broadening of the exciton line above 200 K. This PL peak does not shift with the change in excitation power, while the integrated intensity increases exponentially with the increase in excitation power, i.e., IPL∝Iex1.21, indicating the competition between the radical recombination process and the nonradical recombination process of photogenerated carriers. The FWHM remains unchanged when the excitation power was varied from 0.5 to 50 W cm−2, and then increases exponentially when the excitation power exceeds 50 W cm−2. However, the PL peak consists of four exciton subpeaks, and these subpeaks do not broaden. The PL peak is found to broaden due to recombination competition among the four kinds of excitons. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1391213
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic band structures of GaInNAs/GaAs compressive strained quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 843-847 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic structures of the Ga1−xInxNyAs1−y/GaAs compressive strained quantum wells are investigated using 6×6 k⋅p Hamiltonian including the heavy hole, light hole, and spin-orbit splitting band. By varying the well width and mole fraction of N in the well material, the effects of quantum confinement and compressive strain are examined. The curves of dependence of transition energy on well width and N mole fraction are obtained. The valence subband energy dispersion curves and TE and TM squared optical transition matrix elements of three possible quantum well structures for emitting 1.3 μm wavelength are given. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378336
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative study on the effects of ion density and ion energy on diamond-like carbon deposited by electron cyclotron resonance chemical vapor deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4830-4835 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diamond-like carbon films were deposited using electron cyclotron resonance (ECR) chemical vapor deposition incorporated with a screen grid under different dc bias voltages to compare the effect of ion density and ion energy on the film properties. Langmuir probe measurements and optical emission spectroscopy were used to characterize the ECR plasma, while the films were characterized using Raman and infrared (IR) spectroscopies, hardness, and optical gap measurements. The plasma measurements showed that the ion density, hydrogen atom density, and CH density decreased monotonously following increase in the dc bias voltage. Raman spectra and optical gap measurements indicate the films became more graphitic with lower content of sp3-hybridized carbon atoms as the dc bias voltage was increased. An increase in hydrogen content was found in films prepared at relatively high dc bias voltage, as indicated by IR measurements. Films deposited at −150 V exhibit maximum hardness. The results show the ion density has a stronger effect on the film deposition rate and hydrogen content, while the ion energy affects the film properties more predominantly by changing the bonding structure. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359163
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  • 4
    Electronic Resource
    Electronic Resource
    Model for InGaP/GaAs/InGaP double heterojunction bipolar transistor (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3464-3468 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current–voltage characteristics of an InGaP/GaAs/InGaP double heterojunction bipolar transistor (DHBT) are modeled where the tunneling effect at the base–collector (B–C) junction and base–emitter (B–E) junction is taken into account. Therefore, this model can be applied to both conventional DHBT and composite collector heterojunction bipolar transistor. The role of the n−GaAs layer and n+InGaP layer are discussed and the effects of variation in the doping level and thickness of these layers are considered in the model. Good agreement between our predictions of the model and reported experimental results is achieved. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343888
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of Si doping in In0.52Al0.48As layers grown lattice matched on InP substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1812-1817 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The characteristics of Si-doped In0.52Al0.48As layers as a function of silicon doping ranging from 1×1017 to 4×1018 cm−3 are analyzed by low-temperature photoluminescence (PL), Raman spectroscopy, and Hall effect measurements. When the sample temperature is increased from 4 K, the PL peak energy exhibits an inverted S-shaped dependence which is characteristic of carrier localization. This effect was more prominent at lower doping levels, but weakened at high doping levels due to a possible reduction in the donor binding energy. The peak energy variation at temperatures higher than ≈100 K follows the usual band-edge variation with temperature, suggesting that the PL arises from band-to-band transitions. While the PL linewidth of the undoped and moderately doped samples decreases and then increases with temperature, a near-monotonic increase in the linewidth due to thermal broadening was observed in highly doped samples. Supported by observations of a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360214
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  • 6
    Electronic Resource
    Electronic Resource
    Sequential tunneling in GaAs/AlGaAs multiquantum well structures grown by molecular beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2868-2871 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sequential tunneling of electrons through Schottky diodes with GaAs/AlGaAs multiple quantum wells (MQWs) is reported. Two series of tunneling structures were observed in low-temperature current-voltage (I-V) characteristics in 200-A(ring)-period MQWs. The oscillations in the conductance (G) were found to be persistent from 5 K up to 200 K. S-shape features in the current-voltage characteristics similar to those observed from double-barrier resonant tunneling structures were observed at low temperature in the MQW structures. The electron tunneling process through the MQW structures is discussed in terms of the creation and propagation of high-field domains as a function of the applied bias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357524
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  • 7
    Electronic Resource
    Electronic Resource
    Photoluminescence studies of strained InxGa1−xAs-Al0.28Ga0.72As heterostructures grown by molecular-beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 246-250 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature photoluminescence measurements were carried out on pseudomorphically strained InxGa1−xAs-Al0.28Ga0.72As ternary-on-ternary heterostructures grown by molecular-beam epitaxy to investigate the change in the transition energy and linewidth as a function of InGaAs well thickness at two different indium compositions x=0.10 and x=0.15, respectively. Sharp exciton peaks as narrow as 4–6 meV were observed from the InGaAs wells grown at 530 °C with 1 min of growth interruption at the top and bottom heterointerfaces. The linewidth decreases as the well thickness is increased up to 300 A(ring). In addition, there are signs of linewidth broadening at higher well thicknesses which may indicate the onset of plastic relaxation. Relatively small variations in the transition energy were observed at well thicknesses which are above the theoretical critical thickness as calculated by the Matthews–Blakeslee model [J. Cryst. Growth 27, 118 (1974)], suggesting the existence of a second critical thickness higher than the theoretical value. Good agreement between experimental and calculated transition energy versus well thickness data was obtained, from which the conduction-band offset ΔEc/ΔEg was estimated to be 0.65±0.05 for x=0.10–0.15, consistent with the results derived from other techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357135
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  • 8
    Electronic Resource
    Electronic Resource
    Thickness dependence of density of gap states in diamond films studied using space-charge-limited current (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5747-5753 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and electrical characteristics of chemical vapor deposited (CVD) diamond films have been studied as a function of film thickness. The samples comprise a set of codeposited, nominally undoped diamond films with average grain size on the growth surface increasing linearly with the film thickness. Raman scattering analysis reveals a decrease of nondiamond phase and intragrain defects with increasing film thickness. Temperature dependent dc conductivity results indicate that, as the film thickness increases, the Fermi level moves towards the valence band. There is a corresponding decrease in the density of states at the Fermi level, as deduced from the space-charge-limited current in the bulk of the samples. The spatial variation in the density of states through the material closely reflects the changes observed in the structural and electrical properties of the films. Such characteristic has the implication on the application of CVD diamond in the area of electronics. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360222
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  • 9
    Electronic Resource
    Electronic Resource
    Conduction mechanism in molybdenum-containing diamond-like carbon deposited using electron cyclotron resonance chemical vapor deposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4191-4195 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conduction mechanism of molybdenum-containing (Mo) diamond-like carbon films deposited using electron cyclotron resonance chemical vapor deposition was investigated. It is found that there is a conductivity turning point at around 115 K, above which the conductivity is strongly temperature dependent. This indicates that two types of conduction mechanisms, thermal activation and tunneling coexist in the films, and they dominate the conduction behavior in the high and low temperature regimes, respectively. Within the temperature range investigated, the Poole–Frenkel effect is to be expected for thermal activation. However, due to the low concentration of Mo in the films, this effect was not observable. Tunneling is thought to occur between the Mo clusters or the sp2 clusters. A conductivity model, based on the thermal activation and tunneling, is proposed, and showed good agreement with the results obtained at low field. The conduction behavior at high field is also discussed and some possible mechanisms are proposed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308102
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of process pressure on the growth of hydrocarbon films under direct dc bias in an electron cyclotron resonance plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5277-5282 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of pressure on the deposition of hydrogenated amorphous carbon (a-C:H) thin films using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique are reported. In this study, the ions were accelerated under a constant direct dc bias achieved through a screen grid positioned above the substrate. The deposition pressure was varied to study its effects on the plasma environment under the ECR conditions and also on the properties of the films deposited. It was found that changing the process pressure has a very significant effect on the properties of the films deposited. The hardness and the optical gap of the films were noted to increase with pressure. The sp3 content in the films, as deduced from their Raman spectra, was also observed to increase. The results obtained in this study show that the plasma chemistry, in addition to the ion energy, plays a very significant role in determining the properties of the films deposited. The denser plasma created under the ECR condition at higher pressure, accompanied by the presence of a relatively large amount of atomic hydrogen resulting in enhanced plasma etching of the films, is believed to lead to the results observed. Comparisons have also been made between films deposited under rf induced bias and direct dc bias in the ECR-CVD system. The difference in the characteristics observed can be attributed to the narrower ion energy distribution in the case of direct dc bias. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368815
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