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  • 1
    Electronic Resource
    Electronic Resource
    The effect of reduced growth area by substrate patterning on misfit accommodation in molecular beam epitaxially grown InxGa1−xAs/GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4253-4262 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of reduced growth area on the misfit accommodations of InxGa1−xAs/GaAs grown by molecular beam epitaxy has been studied with cross-sectional transmission electron microscopy (XTEM). Composition grading techniques as well as strained-layer superlattices were used for InxGa1−xAs compositions up to x=0.53 and growth areas which ranged from approximately 10 cm2 (blanket areas) to 4 μm2 squares. Results indicate that the use of step-composition grading and linear-composition grading are particularly effective when combined with reduced growth areas up to 30×30 μm and InxGa1−xAs compositions up to x=0.25. Dislocations which are generated for misfit accommodation during growth are effectively driven to the edges of the patterned growth areas with considerably fewer interactions than dislocations nucleated in blanket areas. XTEM samples prepared from blanket areas were generally found to contain randomly distributed threading dislocation-free regions on the order of 20–30 μm in width bounded by high density dislocation pile-ups. Higher InxGa1−xAs compositions resulted in large densities of threading dislocations with Burgers vectors perpendicular to the growth direction, particularly for step-composition graded layers. We attribute this behavior to roughening of the growth interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348397
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  • 2
    Electronic Resource
    Electronic Resource
    A study of the coupling efficiency versus grating periodicity in a normal incident GaAs/AlGaAs multiquantum well infrared detector (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2105-2109 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of the dependence of coupling quantum efficiency on the grating periodicity of planar metal grating coupled GaAs/AlGaAs quantum well infrared photodetectors has been made in this work. Five different detector samples with grating periodicities of Λ=1.1, 3.2, 5, 7, and 10 μm have been fabricated for the present study. The results showed that the device with a 5 μm grating periodicity gave the best front-side coupling efficiency, which was in good agreement with our theoretical prediction. A single pass quantum efficiency (η) of 11% was achieved for the front-side illumination at λp=9.8 μm and T=77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351597
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental sensitivity analysis of pseudomorphic InGaAs/AlAs resonant-tunneling diodes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6305-6317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Through the use of a novel vertically integrated resonant-tunneling diode (RTD) heterostructure we have established experimentally the relationship between intentional variations in the structural parameters of the pseudomorphic In0.53Ga0.47As/AlAs resonant tunneling diode (i.e., barrier thickness, quantum-well thickness, quantum-well composition, and doping density) and the measured current–voltage characteristics of the device. Based upon the results of these experiments, we have determined that a 1 monolayer increase in AlAs barrier width, InGaAs quantum-well width, or InAs subwell width results in a peak current reduction of 56%±7%, 19%±2%, and 18%±3%, respectively. Further, a 1% decrease in indium mole fraction of the InGaAs quantum well has been found to increase the peak current by 10%±1%. Sensitivity parameters have been tabulated for both the peak current and the peak voltage of the RTD. Through the use of these parameters, the maximum allowed fluctuation in the RTDs structural parameters has been estimated for a given tolerance in the RTDs electrical characteristics. Further, these data can also be used to evaluate the feasibility of in situ epitaxial growth control of resonant tunneling devices. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360511
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  • 4
    Electronic Resource
    Electronic Resource
    Minority carrier magneto-oscillations in the bipolar quantum well resonant tunneling transistor (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2732-2737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magneto-oscillations due to a minority carrier two-dimensional electron gas (2DEG) in the base of a bipolar quantum well resonant tunneling transistor at liquid helium temperatures are reported, we believe, for the first time. These are attributed to a high-density 2DEG formed in the 20 nm undoped setback layer between the base and emitter. The 2DEG density has a nonmonotonic dependence on the emitter/base junction bias, increasing to a maximum at flatband conditions, then decreasing at higher bias. Associated lateral electron diffusion dominates recombination such that the current gain can increase 1000 times in a 6 T magnetic field. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361146
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of AlAs optical constants by variable angle spectroscopic ellipsometry and a multisample analysis (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4677-4687 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using variable angle spectroscopic ellipsometry, optical constants for AlAs (1.4–5.0 eV) are presented which are simultaneously compatible with measured data from four different samples. The below-gap index values are compatible with published prism measured values. The second derivative spectrum are compatible with published values above the direct band gap. The AlAs spectra is Kramers–Kronig self-consistent over the measured range and is compatible with published values from 0.6 to 1.4 eV. The optical constants for thin (〈50 A(ring)) GaAs caps on AlAs are shown to be different from bulk GaAs values and require special consideration when fitting ellipsometric data. For the thin GaAs caps, the E1 and E1+Δ1 critical-point structure is shifted to higher energies as previously observed for GaAs quantum wells. Bulk AlAs optical constants are shown to be different from those of a thin (∼20 A(ring)) AlAs barrier layer embedded in GaAs. The thin barrier layer exhibits a highly broadened critical-point structure. This barrier broadening effect (AlAs) and the thin cap shifting effects (GaAs) have implications for in situ growth control schemes which make use of the E1 and E1+Δ1 critical-point region. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359435
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  • 6
    Electronic Resource
    Electronic Resource
    Studies of thin strained InAs, AlAs, and AlSb layers by spectroscopic ellipsometry (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2663-2674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical constants for thin layers of strained InAs, AlAs, and AlSb have been investigated by spectroscopic ellipsometry and multi-sample analyses. These materials are important for high-speed resonant tunneling diodes in the AlAs/InAs/In0.53Ga0.47As and AlSb/InAs material systems. Understanding the optical properties for these thin layers is important for developing in situ growth control using spectroscopic ellipsometry. Ex situ room-temperature measurements were made on multiple samples. The resulting fitted optical constants are interpreted as apparent values because they are dependent on the fit model and sample structure. These apparent optical constants for very thin layers can be dependent on thickness and surrounding material, and are generally applicable only for layers found in a similar structural context. The critical point features of optical constants for the strained layers and for the thin unstrained cap layers were found to differ from bulk values, and three principle effects (strain, quantum confinement, and thin-barrier critical-point broadening) have been identified as responsible. Of these three, the broadening of the E1 and E1+Δ1 critical points for thin barrier material is the newest and most pronounced. This thin barrier effect is shown to be a separate effect from strain, and is also observable for the AlAs/GaAs system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361137
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  • 7
    Electronic Resource
    Electronic Resource
    A cantilever shadow mask technique for reduced area molecular beam epitaxial growth (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 152-154 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A type of shadow mask growth technique (cantilever shadow masking) for reduced area molecular beam epitaxial growth has been developed and applied to the growth of GaAs and InxGa1−xAs on selective areas of Si and GaAs substrates, respectively. This technique eliminates detrimental sidewall growth interactions, results in precisely positioned growth areas, and can be more readily planarized than other reduced area growth structures. This technique is particularly useful for defect density reduction during latticed-mismatched heteroepitaxy using reduced growth areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104957
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of patterning on defect structure in GaAs grown on Si (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 288-290 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we address the effectiveness of patterned growth in reducing defect density in GaAs on Si. Defect reduction is considered to be subject to the effect of edge profile and the density of defects in initial GaAs islands. Pattern edges (mask edges or large steps) are often the sites for generating microtwins/stacking faults. Mutual interaction of dislocations inhibits the gliding of dislocations to pattern edges, thus affecting the effectiveness of patterned growth in improving the epilayer quality. The study also shows that surface orientation influences the formation of misfit dislocations with a preferred Burgers vector. This observation is interpreted by considering the variation of misfit with different lattice planes across the interface between Si and "tilted'' GaAs lattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103716
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  • 9
    Electronic Resource
    Electronic Resource
    Micro-Raman characterization of structural defects in patterned GaAs-on-Si (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1631-1633 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have applied micro-Raman spectroscopy to the analysis of structural quality of GaAs-on-Si where the GaAs growth was performed through openings in an amorphous mask. The presence of the symmetry forbidden transverse optic (TO) phonon band and line shape of the longitudinal optic (LO) phonon band have been used to extract information concerning the structural quality of microscopic regions of GaAs from the Raman spectra. The utility of TO to LO phonon intensity ratios as a measure of crystal quality has been corroborated by correlation to x-ray rocking curve full width. The structural quality of selectively grown GaAs as determined from first-order Raman ratios is found to degrade in the vicinity of the transition between single crystal and polycrystalline regions. This work also shows that post-growth annealing significantly improves the quality of structures with minimum feature size as small as 2 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104070
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  • 10
    Electronic Resource
    Electronic Resource
    New field-effect resonant tunneling transistor: Observation of oscillatory transconductance (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2742-2744 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present device characteristics of a field-effect, unipolar, resonant tunneling transistor. An oscillatory tunneling current in the transfer characteristics is observed for the first time. Our observation confirms a recent hypothesis that a mere three-to-two dimensional resonant tunneling can occur when scattering rate is less than the attempt frequency of tunneling electrons in the quantum well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101940
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