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  • 1
    Electronic Resource
    Electronic Resource
    The use of graded InGaAs layers and patterned substrates to remove threading dislocations from GaAs on Si (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2697-2702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated threading dislocation (TD) removal from GaAs films on Si by introduction of additional InGaAs graded strain layers in combination with growth on patterned substrates. The substrate patterns consisted of mesas with 10–34 μm widths. The mesa sidewalls were either overhanging (concave), leading to free sidewalls for the film on the mesas, or outward sloping (convex) sidewalls with {111} orientation. The dislocation structure was studied using transmission electron microscopy. It was found that the graded strained layers led to a reduction of dislocation density by a factor of ∼5 in films grown both on mesas with concave sidewalls and on unpatterned substrates. This reduction was due to dislocation reactions leading to annihilation of TDs. For films with graded strained layers on mesas with convex sidewalls, an additional factor of ∼3 reduction in TD density was observed in the part of the film that was grown on top of the mesas. In this case all mobile TDs (TDs associated with 60° misfit dislocations, i.e., TDs that could glide to relieve misfit stress) were removed from the film on top of the mesas to the regions above the sidewalls and only TDs associated with 90° misfit dislocations remained. We suggest that this is due to pinning of the TDs associated with 60° misfit dislocations at the mesa edges and we have presented an explanation for this pinning in terms of the stress conditions at the {111} oriented mesa edges. In addition, this leads us to suggest that in order to obtain minimum TD density it is imperative to prevent formation of 90° misfit dislocation during lattice mismatched heteroepitaxial growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357572
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  • 2
    Electronic Resource
    Electronic Resource
    Si and Si/P implants in In0.5Ga0.5P and In0.5Al0.5P (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3473-3475 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si and Si/P ion implantation doping of In0.5Ga0.5P and In0.5Al0.5P has been studied for several Si and P doses at energies of 90 and 100 keV, respectively. For single Si implants in InGaP a maximum Hall sheet electron concentration of 1.33×1013 cm−2 is achieved for a Si dose of 5×1013 cm−2. When an optimum dose (2.5×1013 cm−2) P coimplant is performed this electron concentration is increased by 65%. The same dose Si implants in InAlP show a maximum effective activation of 3.9% with no P coimplantation and 5.2% with a P-implant dose 1.5 times the silicon dose. The apparent donor ionization energies are estimated from variable temperature Hall measurements to be 2–5 meV for InGaP and ∼80 meV for InAlP. The deeper level in InAlP is attributed to the DX level found in the Al-containing material. The reduction in sheet resistance associated with the use of Si/P coimplantation in InGaP containing heterostructures should contribute to significant performance enhancements in HFETs and lasers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115763
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  • 3
    Electronic Resource
    Electronic Resource
    Intersubband transitions in high indium content InGaAs/AlGaAs quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 364-366 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first observation of intersubband transitions in InyGa1−yAs(y=0.3,0.5)/ AlGaAs quantum wells. These quantum wells were grown on a GaAs substrate with a linearly graded InGaAs buffer to achieve strain relaxation before growth of the quantum wells. Measured intersubband transition energies of 316 and 350 meV are among the largest ever reported. Asymmetric step In0.5Ga0.5As/AlGaAs quantum wells designed for second harmonic generation measurements also demonstrate strong intersubband absorption at 224 meV corresponding to the 1-2 transition. With the large conduction band offsets (larger than 800 meV) available in this material system, extension to larger intersubband transitions energies for quantum well photodetector and nonlinear optics applications should be possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110044
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  • 4
    Electronic Resource
    Electronic Resource
    Short wavelength (5.36–1.85 μm) nonlinear spectroscopy of coupled InGaAs/AlAs intersubband quantum wells (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2630-2632 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report short wavelength second-harmonic generation (SHG) spectroscopy of asymmetric coupled In0.6Ga0.4As/AlAs quantum wells (QWs). The QW is designed to show maximum second-order nonlinear susceptibility χ(2) for SHG of 4 and 2 μm wavelengths by single and double resonance effects, respectively. SHG spectroscopy across the midinfrared is measured using both a CO2 and a free electron laser as pumps. The χ(2) of the QW is extracted from interference of the second-harmonic fields from the QW and GaAs substrate, determined by the azimuthal dependence of the SHG power. We measure χ(2) of the QW for harmonic wavelengths between 5.36 and 1.85 μm. This is the shortest wavelength SHG to date by any QW intersubband interaction. Good agreement of experiment with theory for the dispersion of χ(2) for both singly and doubly resonant conversion is observed throughout the midinfrared. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112585
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  • 5
    Electronic Resource
    Electronic Resource
    Short wavelength intersubband transitions in InGaAs/AlGaAs quantum wells grown on GaAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 736-738 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated intersubband transition energies as high as 580 meV (2.1 μm wavelength) in InGaAs/AlGaAs quantum wells (QWs) grown on GaAs substrates. The well width dependence of intersubband transition energies in both In0.5Ga0.5As/Al0.45Ga0.55As QWs and In0.5Ga0.5As/AlAs QWs have been determined. Good agreement of the intersubband transition energies to a single band effective mass model with band nonparabolicity included is found. Experimental studies of buffer and QW growth parameters for optimized intersubband absorption have also been performed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111050
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  • 6
    Electronic Resource
    Electronic Resource
    Doubly resonant second harmonic generation of 2.0 μm light in coupled InGaAs/AlAs quantum wells (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3365-3367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate intersubband absorption and second harmonic generation (SHG) in asymmetric coupled In0.6Ga0.4As/AlAs n-type quantum wells (QWs) grown on a GaAs substrate. Intersubband absorption at 4.1 and 2.1 μm wavelengths, corresponding to the 1 to 2 and 1 to 3 transitions, respectively, are observed. SHG of 2.0 μm light is demonstrated in this doubly resonant QW. This is the shortest wavelength SHG to date in any n-type QW system. The second order nonlinear susceptibility χ(2) is measured using a free electron laser by interference of the second harmonic fields from the QW and substrate. At a pump wavelength of 4.0 μm, a large asymmetry in the SHG power with rotation angle of the sample arising from SHG from the QW is observed, and a χ(2) of magnitude 20±8 nm/V, approximately 100 times that of bulk GaAs, and phase 63°±34° relative to the GaAs substrate is measured. Comparison of both the linear and nonlinear properties to a simple model is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111276
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  • 7
    Electronic Resource
    Electronic Resource
    Tunable mid-infrared generation by difference frequency mixing of diode laser wavelengths in intersubband InGaAs/AlAs quantum wells (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 265-267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate difference frequency generation (DFG) of 8.66–11.34 μm wavelength light in intersubband InGaAs/AlAs quantum wells by mixing of 1.92 μm±25 nm and 2.39 μm±39 nm. The peak DFG second order nonlinear susceptibility χ(2) is measured to be 12±1 nm/V, more than 65 times that of GaAs, at a difference frequency output wavelength of 9.50 μm. The intersubband absorption for the 1–2 and 1–3 transitions is measured to be 9.3 and 2.1 μm, respectively. Second harmonic generation (SHG) of 4.76, 5.12, and 5.36 μm light with a CO2 laser is observed with a peak SHG χ(2) of 52±3 nm/V. Good agreement of experiment with theory is found for both the linear and nonlinear optical properties. This demonstration of mid-infrared DFG opens the possibility for monolithic diode laser pumps and compact waveguide frequency converters as tunable midinfrared sources. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113512
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  • 8
    Electronic Resource
    Electronic Resource
    High quality single and double two-dimensional electron gases grown by metalorganic vapor phase epitaxy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1911-1913 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the metalorganic vapor phase epitaxy (MOVPE) growth of AlGaAs/GaAs two-dimensional electron gases (2DEGs) with mobilities as high as 786 000 cm2/V s at a carrier density of 3.0×1011 cm−2 at 0.3 K. The mobility figures of merit (μ/n3/2) for these 2DEGs are the highest reported to date for MOVPE materials. These 2DEGs also exhibit the fractional quantum Hall effect (FQHE) with minima in longitudinal resistance corresponding to Landau level filling factors 2/3, 4/3, and 5/3. The temperature dependence and carrier density dependence of mobility were characterized, and the mobility was found to vary linearly with carrier density, implying that the mobility is probably limited by background ionized impurity scattering. A delta-doped 2DEG was also compared with uniformly doped 2DEGs and was found to have a slightly higher mobility. Finally, we obtained high mobility in a coupled double 2DEG structure for 2D to 2D tunneling applications. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114374
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  • 9
    Electronic Resource
    Electronic Resource
    Selective oxidation of buried AlGaAs versus AlAs layers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1385-1387 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report significant differences between the properties of buried oxides converted from AlGaAs and AlAs layers using selective wet oxidation. Layers of AlxGa1−xAs with x≥0.96 exhibit crystallographic dependent oxidation rates, while for layers with x≤0.92 the oxidation rate is isotropic. Mesas containing partially oxidized layers of AlAs are unstable to rapid thermal cycling and exhibit excessive strain at the oxide terminus, while mesas containing partially oxidized layers of AlGaAs are robust and lack evidence of strain. Finally, the oxidation of AlGaAs layers, rather than AlAs, is found to provide robust oxide apertures for reliable vertical-cavity surface emitting lasers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117589
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  • 10
    Electronic Resource
    Electronic Resource
    1.4× efficiency improvement in transparent-substrate (AlxGa1−x)0.5In0.5P light-emitting diodes with thin (≤2000 Å) active regions (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2230-2232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Improvement of 1.4× in the external quantum efficiency and luminous efficiency (lm/W) of transparent-substrate (AlxGa1−x)0.5In0.5P/GaP light-emitting diodes is demonstrated. The improvement is accomplished by reducing the thickness of the active layer to ≤2000 Å and increasing the internal quantum efficiency by using multiple thin (≤500 Å) active layers. The maximum luminous efficiency achieved is 73.7 lm/W at λp∼615 nm and the maximum external quantum efficiency is 32.0% at λp∼632 nm. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123810
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