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  • 1
    Electronic Resource
    Electronic Resource
    Interband transitions in InAsxP1−x/InP strained multiple quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1645-1647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the optical study of the interband transitions in InAsxP1−x/InP strained-layer multiple quantum wells grown by gas-source molecular beam epitaxy. Low-temperature photoluminescence, photoluminescence excitation, and room temperature photomodulated transmission measurements were performed to investigate optical interband transitions. In addition to transitions associated with the heavy-hole and the light-hole bands, a transition involved with the spin-orbit split-off band was observed. We also observed spectral linewidth broadening due to compositional inhomogeneity and layer-thickness fluctuations from the sample using short-period superlattices as the well materials. Calculations based on the envelope-function approximation and phenomenological deformation potential theory, including both band nonparabolicity and strain-induced valence-band mixing, were compared with experimental data to identify the optical transitions between quantized states in the wells. We found good agreement between theory and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351683
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  • 2
    Electronic Resource
    Electronic Resource
    Stimulated emission and gain measurements in molecular-beam epitaxially grown CdTe (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6612-6616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stimulated emission has been observed in molecular-beam epitaxially (MBE) grown films of cadmium telluride (CdTe), using a nanosecond pulsed dye laser as an excitation source. The films were 2.0–2.4 μm thick. Stimulated emission (SE) is seen to arise at several energy positions of the spectra. The different SE peaks exhibited different gain values. The gain was measured using the single beam method, by varying the length of excitation. The bulk CdTe sample studied exhibited stronger saturation effects than those seen in the MBE films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348874
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  • 3
    Electronic Resource
    Electronic Resource
    Optical properties of wurtzite GaN grown by low-pressure metalorganic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3691-3696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of optical studies on the properties of GaN grown by low-pressure metalorganic chemical-vapor deposition, with emphasis on the issues vital to device applications such as stimulated emission and laser action as well as carrier relaxation dynamics. By optical pumping, stimulated emission and lasing were investigated over a wide temperature range up to 420 K. Using a picosecond streak camera, the free and bound exciton emission decay times were examined. In addition, the effects of temperature and pressure on the optical interband transitions and the transitions associated with impurity/defect states were studied using a variety of spectroscopic methods, including photoluminescence and photoreflectance. The fundamental band gap of GaN was mapped out as a function of temperature using the empirical Varshni relation. The pressure coefficient of the gap was determined using diamond-anvil pressure-cell technique. The hydrostatic deformation potential for the direct Γ band gap was also derived from the experimental results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361200
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  • 4
    Electronic Resource
    Electronic Resource
    Excitation energy-dependent optical characteristics of InGaN/GaN multiple quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3181-3183 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have systematically studied the optical properties of InGaN/GaN multiple quantum wells (MQWs) at 10 K under different excitation conditions using photoluminescence (PL), PL excitation, and time-resolved PL spectroscopy. We found that the PL emission consists of a strong main peak at 2.80 eV and a much weaker and broader secondary peak at ∼2.25 eV. We observed that the peak position blueshifts and the spectral width narrows for the main peak when the excitation energies are varied from 3.81 eV (above the band gap of the AlGaN capping layer) to 2.99 eV (below the band gap of the GaN barrier layers). The intensity ratio of the main peak to the secondary peak also varied with excitation energy. The two observed emission peaks originate from different layers of the MQWs. Time-integrated and time-resolved PL revealed that the InGaN-related spontaneous emission processes are strongly affected by inhomogeneity and carrier localization in the MQWs. From these studies under varying excitation energies, we conclude that interface-related defects and roughness may play an important role in the InGaN-related emission mechanism during the carrier transfer between different layers of the MQWs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122711
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  • 5
    Electronic Resource
    Electronic Resource
    Erratum: "Recombination dynamics in n-AlxGa1−xAs/n-In0.5Ga0.5P type-II heterostructures" [Appl. Phys. Lett. 73, 1245 (1998)] (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2219-2219 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122431
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  • 6
    Electronic Resource
    Electronic Resource
    Large optical nonlinearities near the band gap of GaN thin films (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1504-1506 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interband optical transitions in single-crystal GaN films grown by metal organic chemical vapor deposition have been studied at 10 K and room temperature using nondegenerate nanosecond optical pump-probe techniques. At low temperatures, strong, well-resolved features are seen in the absorption and reflection spectra corresponding to the 1s A and B exciton transitions. These features broaden and decrease in intensity due to the presence of a high density of photoexcited free carriers and are completely absent in the absorption and reflection spectra as the excitation density, Iexc, approaches 3 MW/cm2, resulting in induced transparency in transmission measurements. The absorption spectra also show induced absorption below the band gap as Iexc is increased. Both the observed induced transparency and induced absorption were found to be extremely large, exceeding 4×104 cm−1 as the pump density approaches 3 MW/cm2 at 10 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121040
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  • 7
    Electronic Resource
    Electronic Resource
    Pressure-dependent photoluminescence study of InxGa1−xN (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2433-2435 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of pressure-dependent photoluminescence (PL) studies of single-crystal InxGa1−xN (0≤x〈0.15) films grown on top of thick GaN epitaxial layers by metalorganic chemical vapor deposition with sapphire as substrates. PL measurements were performed at 10 K as a function of applied hydrostatic pressure using the diamond-anvil-cell technique. The luminescence emissions from the InxGa1−xN epifilms were found to shift linearly toward higher energy with increasing pressure. By examining the pressure dependence of the PL spectra, the pressure coefficients for the emission structures associated with the direct band gap of InxGa1−xN were determined. The values of the pressure coefficients were found to be 3.9×10−3 eV/kbar for In0.08Ga0.92N and 3.5×10−3 eV/kbar for In0.14Ga0.86N. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120083
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  • 8
    Electronic Resource
    Electronic Resource
    Intrinsic exciton transitions in GaN (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 455-461 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intrinsic excitonic transitions in GaN have been studied using a variety of spectroscopic measurements. Sharp spectral structures associated with intrinsic free excitons could be observed in photoluminescence, reflection, and absorption spectra. The energy positions of excitonic transitions in GaN epitaxial layers were found to be influenced by the residual strain resulting from lattice-parameter and thermal-expansion mismatches between the epilayers and the substrates. The values of the four principal deformation potentials of wurtzite GaN were derived by using the strain tensor components determined by x-ray measurements. The observation of spectral features involving the emission of LO phonons in absorption and photoluminescence excitation spectra at energies above exciton resonances indicate that a phonon-assisted indirect excitation process, which simultaneously generates a free exciton and a LO phonon, is a very significant and efficient process in GaN. The lifetime of the free excitons is found to be longer than the relaxation time of LO-phonon emission but much shorter than that of acoustic-phonon emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366660
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of subband mixing and subband dispersion on the exciton line shape of superlattices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1880-1882 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have found a very unusual exciton line shape in the vicinity of n=2 heavy hole states (HH2) of GaAs/AlxGa1−xAs superlattices. The excitonic structure consisting of a step, a sharp peak, and a broad asymmetric hump results from valence-band mixing between HH2 and n=1 light hole states, in conjunction with subband dispersion due to well-to-well coupling of electrons and holes. In quantum well samples with negligible subband dispersion, a distinctly different exciton line shape is observed. The observed line shape is well fitted by a theory recently reported by Chu and Chang [Phys. Rev. B 39, 10861 (1989)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103076
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamics of photoexcited carriers in AlxGa1−xN/GaN double heterostructures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 3158-3160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results of a time-resolved photoluminescence study of the dynamics of photoexcited carriers in AlxGa1−xN/GaN double heterostructures (DHs). The carrier dynamics including generation, diffusion, spontaneous recombination, and nonradiative relaxation were studied by examining the time decay of photoluminescence associated with the spontaneous recombination from the samples. The temporal evolution of the luminescence from the GaN active layers of the DH samples was found to be governed by a carrier–diffusion dominated capture process. The determination of the capture time for the carriers drift and diffusion into the GaN active region, in addition to the effective lifetimes of the spontaneous recombination for carriers in the AlGaN cladding layers and the GaN active region, allows an estimation of the diffusion constants for the minority carriers in the AlxGa1−xN cladding layers of the DHs. Our results yield a diffusion constant of 2.6 cm2/s for Al0.03Ga0.97N and 1.5 cm2/s for Al0.1Ga0.9N at 10 K. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366101
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