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  • 1
    Electronic Resource
    Electronic Resource
    Optical and electrical properties of selectively delta-doped strained InxGa1−xAs/GaAs quantum wells (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2627-2632 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here an investigation of selectively delta-doped strained InGaAs/GaAs quantum wells. Electronic structures of the systems were calculated by self-consistently solving the Schrödinger and Poisson equations and the calculations revealed a systematic variation of the band structure as the delta sheet moved away from the center of the well to the edge and finally to the barrier. The results were found to be in agreement with our photoluminescence (PL) measurements. For center-doped samples, band-gap renormalization was found to be strong from the PL data, and our realistic random-phase approximation calculation for the heavily doped sample is in excellent agreement with the PL data. The radiative lifetimes were measured to be around 450 ps for all the samples, and surprisingly they vary very little from sample to sample although the wave-function overlap was considerably different for some samples. We also report Shubnikov–de Haas (SdH) measurements on the two barrier doped cases. For the heavily doped sample (A12132), two oscillation signals were detected and they were identified as two upper subbands. The measured electron densities were in very good agreement with the self-consistent calculation. Illumination did not make any difference to the measured densities. For the low-doped sample (A12025), however, the measured electron density before illumination is much smaller than the calculated, and illumination was found to make a large difference. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361133
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  • 2
    Electronic Resource
    Electronic Resource
    The temperature dependence of threshold current of chemical beam epitaxy grown InGaAs–InP lasers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1804-1807 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of threshold current between 130 and 310 K of 1.65 μm In0.53Ga0.47As–InP bulk lasers grown by chemical beam epitaxy has been measured. Comparison with a calculation of the spontaneous recombination current at threshold allows one to determine the proportion of current loss over this temperature range. It is found that the loss can be described using an Auger recombination component of the form Rauger=C'n3 exp(−Ea/kBT) where n is the carrier population density in the undoped active region. The activation energy Ea is found to be 39±5 meV which is in excellent agreement with the theoretical value for the conduction to heavy hole band/split-off to heavy hole band Auger process. The values obtained for the Auger coefficient C over the temperature range are in close agreement with published values obtained by time resolved photoluminescence. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360212
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature dependence of the lasing wavelength of InGaAs quantum dot lasers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4859-4861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We observe that the emission wavelength of edge-emitting InGaAs quantum dot lasers has a much weaker temperature dependence (0.6 Å K−1) than equivalent quantum well devices (3 Å K−1). Measured gain and absorption spectra show that the gain peak wavelength due to dot states is almost independent of temperature for a given value of peak gain whereas the absorption edge shifts at a rate of about 2 Å K−1. Above 100 K the occupancy of dot states can be described by Fermi functions and on this basis we find that the measured gain and absorption spectra are in excellent quantitative agreement. Although the band edge energy reduces with increasing temperature, this analysis shows that the energy distribution of dot states matches the evolution of the Fermi functions such as to leave the quasi Fermi level separation and the wavelength of the gain peak unchanged as a function of temperature for a given value of peak gain. This energy distribution is a consequence of the dot size distribution so the match to the Fermi functions is probably fortuitous. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402666
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of optical absorption in epitaxial semiconductor layers by a photovoltage method (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2288-2295 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method has been developed for measuring optical absorption in epitaxial semiconductors in which the layer structure is grown on a substrate of narrower band gap and opposite conductivity-type so that the intensity of light transmitted can be monitored by measuring the photovoltage generated at the buried junction using a transparent surface contact. This arrangement provides a quick method of locating the wavelengths of features in the absorption spectrum. However, it is also possible to obtain an absolute measurement of the transmitted fraction using a control sample from which the absorbing layer structure has been removed by etching, usually a matter of etching only a few microns. This result is independent of surface reflections and the linearity and spectral response of the junction. The method is described with particular reference to GaAs/AlGaAs multiple quantum well structures, though it is also applicable to single homogeneous layers, and the experimental results are in good agreement with those obtained by conventional transmission measurements on samples from which the substrate has been removed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335948
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement and calculation of spontaneous recombination current and optical gain in GaAs-AlGaAs quantum-well structures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1144-1156 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental determinations have been made of the peak optical gain as a function of spontaneous recombination current density for GaAs quantum wells of width 25 and 58 A(ring) bounded by AlGaAs barriers. These data were obtained from measurements of spontaneous emission spectra, observed through narrow windows in the 50-μm-wide contact stripes of oxide isolated lasers, using only a single reference value of the optical absorption coefficient above the band edge to calibrate the measurements in absolute units. These results are in good agreement with gain-current curves calculated using a model which includes unintentional monolayer well width fluctuations, band-gap narrowing and intraband carrier-carrier scattering. The characteristic intraband scattering time is calculated from first principles as a function of electron energy and carrier density on the basis of a 2-dimensional Auger-type process. This lifetime gives a much better representation of our observed spontaneous spectra than a lifetime which is simply dependent upon carrier density. The comparison between experiment and model calculation involves no adjustable parameters. For the 58-A(ring)-wide wells there is a difference between the experimental and calculated gain-current curves at low values of gain. We show that this is a consequence of applying the Einstein relations to a broadened spectrum in the process of deriving the gain from the observed spontaneous emission spectrum. A direct comparison of the shapes of experimental and calculated spontaneous emission spectra at several injection levels provides a more rigorous, yet equally valid, verification of the computer model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349622
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure dependence of the nonradiative lifetime in GaAs/AlGaAs double-heterostructure lasers (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3448-3450 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the linear losses in a GaAs/AlGaAs double-heterostructure laser as a function of applied hydrostatic pressure. The nonradiative lifetime increases by a factor 2.5 from zero to 7.6 kbar, and if this is due to recombination via a deep state, then the rate-limiting capture cross section decreases with pressure, suggesting capture by multiphonon emission. We find that it is necessary to postulate the existence of other nonlinear losses at threshold to account for the increase in threshold current with pressure measured on the same structure. Carrier transfer to higher conduction-band minima in the active or cladding regions are suggested as possible mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339313
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature dependence of threshold current in GaAs/AlGaAs quantum well lasers (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 599-601 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the threshold current and its temperature (T) dependence in the range 200–400 K for AlGaAs quantum well lasers with 25-A(ring)-wide GaAs wells using a model which includes lifetime broadening of the transitions and broadening of the density of states function by fluctuations in the well width. The threshold current varies approximately linearly with T and the principal effect of broadening is to increase the threshold current causing a reduction in the fractional change of current with temperature. The apparent value of the parameter T0 is increased to ≈400 K, compared with ≈320 K without broadening. The calculations are compared with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99647
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  • 8
    Electronic Resource
    Electronic Resource
    Recombination processes in quantum well lasers with superlattice barriers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2380-2382 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spontaneous emission spectra from GaAs quantum well lasers grown by molecular beam epitaxy show that the radiative recombination rate in (AlAs)(GaAs) superlattice barriers is greater than in alloy barriers of the same average composition (x=0.25) due to reduction in effective gap by superlattice effects. Measurements of emission spectra as functions of temperature show that these radiative processes account for a significant part of the temperature variation of the threshold current and we estimate that the nonradiative lifetime in the superlattice barriers is an order of magnitude longer than in alloy barriers grown under similar conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102023
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  • 9
    Electronic Resource
    Electronic Resource
    Short-period (AlAs)(GaAs) superlattice lasers grown by molecular beam epitaxy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 299-301 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used short-period all-binary (AlAs)(GaAs) superlattices with layers as thin as three monolayers to synthesize the barrier and cladding regions of GaAs quantum well lasers grown by molecular beam epitaxy. By studying the threshold current of single- and double-well devices as a function of cavity length and temperature, we conclude that the optical scattering losses are very low, that the gain-current characteristics are similar to alloy barrier devices, and that there is evidence for current leakage by recombination in the barriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99901
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  • 10
    Electronic Resource
    Electronic Resource
    Spontaneous recombination current in InGaAs/GaAs quantum well lasers (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1482-1484 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the intrinsic factors which determine the threshold current and its temperature dependence in 160-A(ring)-wide In0.2Ga0.8As single well quantum lasers with GaAs barriers, grown by molecular beam epitaxy on GaAs substrates. By measuring the relative temperature dependence of the spontaneous emission intensity at threshold we show that radiative transitions between higher order (n=2,3) electron and heavy hole subbands make a significant contribution to the threshold current and its temperature sensitivity, even in devices where the laser transitions are between n=1 subbands. These higher transitions will also influence the dependence of threshold current and its temperature sensitivity on well width.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103370
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