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  • 1
    Electronic Resource
    Electronic Resource
    Optical properties of (AlxGa1−x)0.52In0.48P at the crossover from a direct-gap to an indirect-gap semiconductor (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2241-2249 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical properties and the dynamics of excitons and the electron-hole plasma have been studied in disordered (AlxGa1−x)0.52In0.48P near to the direct-to-indirect band gap crossover. In particular we have investigated three epitaxial layers grown by solid-source molecular beam epitaxy with varying Al content x. Two of them have compositions in the immediate vicinity of the crossover point, the other is assigned to the indirect-gap regime. Both direct and indirect recombination processes contribute to the photon emission from the material. Since the relative importance of the different recombination processes depends strongly on temperature, excitation intensity, and excitation pulse duration, the processes can be identified by changing these parameters. As a result, we can determine the relative alignment of the conduction band minima and the distribution of the electrons among them. At high excitation levels the two crossover samples show stimulated emission at a photon energy of ∼2.29 eV, i.e., in the green spectral range. Using the variable stripe length method, we find an optical gain of up to ∼600 cm−1 at excitation levels of ∼350 kW/cm2. Stimulated emission involves direct recombination. This conclusion is reached from the experiments and from line-shape modeling, including a self-consistent treatment of populations and renormalization of the conduction band minima. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366963
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  • 2
    Electronic Resource
    Electronic Resource
    Optically pumped, indirect-gap $Al_{\rm x}Ga_{1-{\rm x}}As$ lasers (1996)
    Springer
    Applied physics 64 (1996), S. 73-76 
    Details
    ISSN: 1432-0630
    Keywords: PACS42.70.Hj; 78.55.Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. We demonstrate optically pumped lasers with active layers of indirect-gap Al $_{\rm x}$ Ga $_{1-{\rm x}}$ As operating up to room temperature. The emission wavelength is 609 nm at 20 K and 639 nm at 300 K, respectively. The laser threshold shows a weak sensitivity on the lattice temperature. The relevant parameters of the lectron-hole plasma close to threshold are determined from gain spectroscopy using the variable stripe-length method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050446
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  • 3
    Electronic Resource
    Electronic Resource
    Linear and nonlinear optical studies of CdS1−x Se x quantum dots (1991)
    Springer
    The European physical journal 20 (1991), S. 345-348 
    Details
    ISSN: 1434-6079
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this contribution we present and discuss our measurements on CdS1−x Se x quantum dots in a glass matrix. In linear absorption measurements we find the typical blue shift of the transitions with decreasing crystallite radius due to quantization. The luminescence shows a significant Stokes shift with respect to absorption, which is interpreted in terms of strong exciton-phonon coupling and allows to deduce the Huang-Rhys factor S. Under high excitation we find an additional emission band on the high energy side, which can be attributed to the recombination of an excited two electron-hole pair state to a one electron-hole pair state in agreement with theory. Pump and probe beam experiments give a bleaching but no hole burning. Finally we discuss some open questions especially concerning the high energy structures in the absorption spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01544007
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