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  • 1
    Electronic Resource
    Electronic Resource
    Normal-incidence electroabsorption in Ga1−xAlxSb/AlSb L-valley quantum wells for 3–5 μm optical modulation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2810-2812 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical investigations are presented of the electric-field dependence of normal-incidence interconduction subband absorption in Ga1−xAlxSb/AlSb L-valley quantum wells. Under an applied electric field of 50 kV/cm, a blue shift of the absorption peak from 4.94 to 4.82 μm was found in a Ga0.7Al0.3Sb/AlSb structure with well width of 25 A(ring). The ability to absorb normally incident light and to achieve significant Stark shifts with bias makes the Ga1−xAlxSb/AlSb L-valley system an attractive choice for the 3–5 μm vertical optical modulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354630
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of energy gap and band structure on free-carrier nonlinear susceptibilities in semiconductors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4317-4321 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using dispersion relations from the Kane band model, we obtain limiting forms for the third-order nonlinear susceptibilities due to nonparabolicity, thermal-carrier generation, and nonequilibrium optical-carrier generation. We show that whereas χ(3)'s for all three processes increase with decreasing energy gap, there is no further benefit once Eg becomes smaller than either the Fermi or thermal energies. In fact, simultaneous optimization of both the magnitude of χ(3) and the saturation properties favors materials with a large direct gap and large effective mass, coupled with a smaller thermal gap which may be indirect in either real or momentum space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349110
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  • 3
    Electronic Resource
    Electronic Resource
    Anisotropic screening and ionized impurity scattering in semiconductor superlattices and multiple quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6676-6685 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a general theoretical treatment of ionized impurity scattering in semiconductor superlattices. Employing an extension of the quasi-two-dimensional calculations of Stern and Howard to multi-well structures, we explicitly account for nonuniformity of the wavefunction distribution function, arbitrary dispersion relations, scattering by impurities in neighboring periods, and screening by electrons in neighboring wells. Interperiod phenomena are found to be quite significant whenever the screening length is comparable to or longer than the distance between the quantum wells. Calculated results are compared with recent data for modulation-doped and setback-modulation-doped HgTe-CdTe superlattices. However, the discussion emphasizes general aspects of the problem rather than features specific to a particular system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355338
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  • 4
    Electronic Resource
    Electronic Resource
    Enhancement of intersubband Stark effects in L-valley step quantum wells for infrared modulation and voltage tunable detection (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1195-1198 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a new type of optical modulator employing two-step Ga1−xAlxSb/Ga1−yAlySb/Ga1−zAlzSb L-valley quantum wells to enhance the Stark shifts of the intersubband transition energy and therefore to achieve large absorption spectral changes with applied bias. Due to the effective-mass anisotropy of electrons in the L-valleys and the tilted growth direction with respect to the valleys, this novel structure can intrinsically absorb normal incidence light. Under an electric field of 50 kV/cm, a blue shift of the absorption peak from 10.9 to 9.8 μm was found from our calculations in a Ga0.7Al0.3Sb/Ga0.5Al0.5Sb/Ga0.4Al0.6Sb structure with a Ga0.7Al0.3Sb well width of 25 A(ring) and a Ga0.5Al0.5Sb step width of 25 A(ring). The ability to absorb normally incident light and to achieve significant Stark effects with bias makes this structure an attractive choice for such high-speed optoelectronic devices as vertical infrared light modulators and voltage tunable photodetectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354920
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  • 5
    Electronic Resource
    Electronic Resource
    Auger recombination in HgCdTe quantum wires and quantum boxes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3394-3398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum-wire and quantum-box structures for narrow-gap materials with small effective masses, such as HgCdTe, can readily be fabricated using current lithographic techniques. In this article, we calculate the Auger-recombination carrier lifetimes in HgCdTe quantum-wire and quantum-box structures, with band gaps in the 2–5 μm wavelength range. Quantum confinement is generally believed to increase the carrier lifetimes. However, we find the Auger recombination lifetime in a HgCdTe quantum wire is shorter than that in a quantum well, and it decreases as the wire width decreases because of the corresponding increase in the density of states. On the other hand, band-to-band Auger recombination is zero in a quantum box because the overlap functions vanish and because of the discrete nature of the energy levels. Therefore, within the confines of our model, we can expect improved temperature performance from long-wavelength quantum-box lasers but not from quantum-wire lasers. Furthermore, these conclusions are applicable for all types of band-to-band Auger processes and semiconductor materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350935
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  • 6
    Electronic Resource
    Electronic Resource
    Band parameters for III–V compound semiconductors and their alloys (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5815-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1368156
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  • 7
    Electronic Resource
    Electronic Resource
    High-speed spin-polarized intersubband lasers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4734-4739 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin-polarized intersubband lasers based on optically pumped type-II antimonide quantum wells in a magnetic field are proposed. Complete discretization of the electron energy spectrum is predicted to extend the electron lifetime considerably. Continuous-wave room-temperature operation is projected for both interband and intersubband pumping configurations lasing at λ=16–24 μm. Furthermore, the parasitic capacitances associated with electrical injection are eliminated, and the large differential gain and fast intrinsic time scale should give modulation bandwidths in excess of 100 GHz. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371437
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  • 8
    Electronic Resource
    Electronic Resource
    Photo-Hall analysis for inhomogeneously excited semiconductors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4638-4644 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A more rigorous numerical method for determining bulk semiconductor transport properties from photo-Hall data is presented and is used to determine compensation densities in narrow-gap HgCdTe. Previous studies have treated carrier density inhomogeneities by means of a two-layer approach, assuming a photoexcitation layer of constant thickness associated with either the absorption depth or the ambipolar diffusion length. Here, we show that this approximation can lead to significant error. For arbitrary optical intensities a more detailed integration over depth is required, properly accounting for the variation in the optical and transport of the material with carrier density and optical intensity. In the present technique, the spatial profile of the carrier density, n(z), is calculated as a function of optical intensity Φ0. The electron mobility μ is expanded in known functions of the carrier density. By using this n(Φ0,z) and μ(n), integral expressions for the net conductivity and Hall coefficient are then evaluated. The unknown coefficients in the mobility expansion are varied parametrically to obtain the best fits to the measured Hall coefficient and conductivity as a function of optical flux. From this fit, the electron mobility is determined as a function of carrier density. Detailed sample calculations are performed for the case of narrow-gap, n-type Hg1−xCdxTe at low temperatures assuming 10.6 μm CO2 laser excitation. Analysis of the photo-Hall data using the improved method leads to a reliable determination of compensation densities in this material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335374
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  • 9
    Electronic Resource
    Electronic Resource
    Intersubband all-optical limiter based on thermally induced intervalley transfer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7662-7665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose an all-optical limiter based on the thermally induced intervalley transfer of electrons from Γ-valley states with forbidden normal-incidence intersubband interactions to L-valley states which absorb strongly. Detailed modeling of the device performance in the short-pulse regime (≤100 ns) yields that the output intensity for a limiter with only 10% insertion loss at low excitation levels will remain clamped over a dynamic range of 25–40.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365344
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  • 10
    Electronic Resource
    Electronic Resource
    Infrared electroabsorption modulation at normal incidence in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 92-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A normal-incidence modulation mechanism is proposed which uses the Stark effect to induce Γ-L transitions in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (QWs). A significant feature of this structure is the unusual band alignments which localize two deep wells for the Γ and L bands in adjacent layers, i.e., the Γ-valley minimum is in the InAs while the L-valley minimum is in the GaSb. In contrast to a square QW, where the Stark shifts for both Γ and L subbands are in the same direction, the two step wells for Γ and L valleys in the proposed structure are oppositely biased in the presence of an electric field. Therefore, the first Γ and L subbands move toward each other, making the Γ-L crossover occur more efficiently. Near this point, most of the Γ electrons transfer to the L valleys, where they are allowed to make intersubband transitions under normally incident radiation. As a result, the device switches from being transparent to normal-incidence light to strongly absorbing it. The calculations indicate that excellent on/off ratios can be achieved in this structure operating at T≤150 K with electric fields on the order of ∼100 kV/cm for any infrared wavelength within the range of 3–20 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357065
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