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  • 1
    Electronic Resource
    Electronic Resource
    Deep electron traps in GaAs/n-AlxGa1−xAs single-quantum wells (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2408-2414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep-level-transient spectroscopy on molecular-beam epitaxially grown square GaAs/ n-AlxGa1−x As (x=0.24–0.39) single-quantum wells shows a series of electron traps in the AlGaAs with energies EC−ET at 0.12, 0.22, 0.29, 0.52, and 0.63 eV and with concentrations of about 5×1015 cm−3. The defects are located in the upper AlGaAs layer near the GaAs well layer. The trap concentrations and the widths of the spatial trap distributions (typically 15 nm) are independent of the well width. For all traps, a nonexponential capture process which is logarithmic in time is observed. Time-dependent depth profiling shows a virtual shift of the trap distribution to the surface for shorter filling pulses. Both effects are due to the nonabrupt depletion edge (Debye tail). No direct emission from the quantum wells is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341674
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  • 2
    Electronic Resource
    Electronic Resource
    SI GE TECHNOLOGY: Heteroepitaxy and High-Speed Microelectronics (2000)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 30 (2000), S. 335-362 
    Details
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We review recent advances in our understanding of the epitaxial growth and properties of SiGe/Si heterostructures for applications in high-speed field-effect transistors. Improvements in computing power and experimental methods have led to new calculations and experiments that reveal the complexity of 60o misfit dislocations and their interactions, which ultimately determine the characteristics of strain-relaxed SiGe films serving as a buffer layer for strained-layer devices. Novel measurements of the microstructure of relaxed SiGe films are discussed. We also present recent work on the epitaxial growth of SiGe/Si heterostructures by ultra-high-vacuum chemical vapor deposition. This growth method not only provides device quality buffer layers, but abrupt, high-concentration phosphorous-doping profiles, and high-mobility S0.20Ge0.80/Ge composite hole channels have also been grown. These achievements enabled the fabrication of outstanding n- and p-channel modulation-doped field-effect transistors that show enormous promise for a variety of applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.matsci.30.1.335
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  • 3
    Electronic Resource
    Electronic Resource
    Assessment of oxygen in gallium arsenide by infrared local vibrational mode spectroscopy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1442-1444 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two infrared local vibrational mode (LVM) absorption lines occurring at 715 and 845 cm−1 shift to 679 and 802 cm−1 in gallium arsenide doped with 18O, proving that the lines arise from the vibrations of oxygen impurities. The 715 cm−1 line exhibits a triplet 69,71Ga isotope fine structure consistent with that expected from a quasi-substitional VAs-O center. The 845 cm−1 line appears as a closely spaced doublet expected for a bonded interstitial oxygen atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100691
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  • 4
    Electronic Resource
    Electronic Resource
    Unique x-ray diffraction pattern at grazing incidence from misfit dislocations in SiGe thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 89-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grazing-incidence x-ray diffraction (GIXD) permits the direct measurement of in-plane lattice parameters of SiGe films that are too thin to yield good results from normal-geometry triple-axis techniques. A unique "X''-shaped pattern has been seen in H–K reciprocal space maps of diffracted x-ray intensity from SiGe films that have relaxed via a modified Frank–Read mechanism. Contours of intensity are seen along the 〈110〉 directions from the (4¯00) reciprocal lattice peak with the introduction of the first dislocations. For higher dislocation densities the X-shaped contours are anisotropically distorted and a satellite peak, corresponding to the lattice parameter for a partially relaxed film, becomes identifiable at lower H. In contrast, H–K reciprocal-space contours from thin SiGe films that have relaxed by roughening and subsequent random nucleation of dislocations display broad, oval-shaped contours centered at the (4¯00) reciprocal lattice point for the film. Numeric simulations of GIXD from a variety of dislocation arrangements were performed in order to understand the origin of the X pattern. We show that this pattern arises from an array of long misfit dislocations running in the 〈110〉 directions. The anisotropic distortion of the X pattern arises at higher dislocation densities from orthogonal intersections of dislocations with equal Burgers vector, which are characteristic of dislocation networks generated by the modified Frank–Read mechanism. We also verify that the measured values of the in-plane lattice parameter, together with the out-of-plane lattice parameter determined from the symmetric (004) reflection, lead to accurate calculation of the composition and strain in these SiGe layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362776
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  • 5
    Electronic Resource
    Electronic Resource
    Dislocation nucleation barrier in SiGe/Si structures graded to pure Ge (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2845-2847 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution triple-axis x-ray diffraction measurements were used to study strain relaxation in the individual layers of a SiGe/Si structure step-graded to pure Ge. The tilt of each layer is explained by extending the model previously proposed for obtaining the nucleation activation energy of dislocations to account for the reduced miscut of the growth surface as the sample relaxes and the variation in the materials properties with alloy composition. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112511
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  • 6
    Electronic Resource
    Electronic Resource
    Nucleation of dislocations in SiGe layers grown on (001)Si (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3968-3977 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive x-ray-diffraction study of the variation of the tilt angle between a Si1−xGex layer and the (001) Si substrate is presented. Such measurements provide the basis of a new method for determining the nucleation activation energy of misfit dislocations. A detailed model, independent of the particular relaxation mechanism, is derived which relates the tilt angle to the nucleation activation energy on the different slip systems and to the density of misfit dislocations. The model has been applied to the modified Frank–Read mechanism observed in graded samples. Relaxation occurs in such samples for strain in the range 0.002≤ε≤0.006 with an activation energy of about 4 eV. The critical thickness for growth of a strained layer is shown to be smaller when the substrate is miscut than when it is well oriented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356992
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of alloy composition and strain in thin GexSi1−x layers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8098-8108 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The utility of Raman spectroscopy for the simultaneous determination of composition and strain in thin GexSi1−x layers has been investigated. Using data from the literature and new data for the strain shift of the Si-Si phonon mode presented here, we show how Raman spectra provide several different means of measuring composition and strain in samples as thin as 200 A(ring). We demonstrate that for largely relaxed layers with compositions near x=0.30, Raman scattering can measure the composition, x, with an accuracy of ±0.015 and the strain, ε, with an accuracy ±0.0025. The accuracy of the alloy composition obtained from Raman spectra is comparable or, in the case of very thin layers, superior to that measured by other techniques such as x-ray diffraction, electron microprobe, and Auger electron spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356554
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of indium on the properties of DX centers in Si-doped Iny(Ga0.3Al0.7)1−yAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1674-1681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The addition of In to Si-doped Al0.3Ga0.7As has been investigated to determine its effect on DX centers. As expected, the persistent photoconductivity of the material is reduced as the band gap decreases with increasing In concentration. In addition, a new deep level transient spectroscopy peak is observed for the first time, which we attribute to DX centers having near In neighbors. This is clear evidence that the DX levels are highly localized states associated with donor impurities, whose properties are very sensitive to the local atomic configuration near the donor atom. This work supports previously published work on the effects of alloy disorder on DX centers, which is the strongest evidence to date for the microscopic configuration of the DX level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346651
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  • 9
    Electronic Resource
    Electronic Resource
    Deep donor levels (DX centers) in III-V semiconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: DX centers, deep levels associated with donors in III-V semiconductors, have been extensively studied, not only because of their peculiar and interesting properties, but also because an understanding of the physics of these deep levels is necessary in order to determine the usefulness of III-V semiconductors for heterojunction device structures. Much progress has been made in our understanding of the electrical and optical characteristics of DX centers as well as their effects on the behavior of various device structures through systematic studies in alloys of various composition and with applied hydrostatic pressure. It is now generally believed that the DX level is a state of the isolated substitutional donor atom. The variation of the transport properties and capture and emission kinetics of the DX level with the conduction-band structure is now well understood. It has been found that the properties of the deep level when it is resonant with the conduction band, and is thus a metastable state, are similar to its characteristics when it is the stable state of the donor. And it has been consistently found that there is a large energy difference between the optical and thermal ionization energies, implying that this deep state is strongly coupled to the crystal lattice. The shifts in the emission kinetics due to the variation in the local environment of the donor atom suggest that the lattice relaxation involves the motion of an atom (the donor or a neighboring atom) from the group-III lattice site toward the interstitial site. Total energy calculations show that such a configuration is stable provided that the donor traps two electrons, i.e., has negative U. Verification of the charge state of the occupied DX level is needed as well as direct evidence for its microscopic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345628
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  • 10
    Electronic Resource
    Electronic Resource
    The capture barrier of the DX center in Si-doped AlxGa1−xAs (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 4786-4797 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the capture barrier for the DX center in Si-doped AlxGa1−xAs as a function of the alloy composition. A model of the capture process which requires a distribution of capture barrier heights has been fit to the data for samples with x=0.35. A simple technique is used to extract the average capture barrier height from data for samples with AlAs mole fraction ranging from x=0.27 to x=0.55. The barrier height varies strongly with the composition and has a minimum at x=0.35. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338981
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