Browsing by Author "Merritt, T. R."

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    Dynamics of photoexcited carriers and spins in InAsP ternary alloys
    Meeker, M. A.; Magill, Brenden A.; Merritt, T. R.; Bhowmick, M.; McCutcheon, K.; Khodaparast, Giti A.; Tischler, J. G.; McGill, S.; Choi, S. G.; Palmstrom, C. J. (AIP Publishing, 2013-06)
    The recent rapid progress in the field of spintronics involves extensive measurements of carrier and spin relaxation dynamics in III-V semiconductors. In addition, as the switching rates in devices are pushed to higher frequencies, it is important to understand carrier dynamic phenomena in semiconductors on femtosecond time-scales. In this work, we employed time and spin resolved differential transmission measurements; to probe carrier and spin relaxation times in several InAsP ternary alloys. Our results demonstrate the sensitivity of the spin and carrier dynamics in this material system to the excitation wavelengths, the As concentrations, and temperature. (C) 2013 AIP Publishing LLC.
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    Photoluminescence lineshape and dynamics of localized excitonic transitions in InAsP epitaxial layers
    Merritt, T. R.; Meeker, M. A.; Magill, Brenden A.; Khodaparast, Giti A.; McGill, S.; Tischler, J. G.; Choi, S. G.; Palmstrom, C. J. (American Institute of Physics, 2014-05-21)
    The excitonic radiative transitions of InAsxP1-x (x = 0.13 and x = 0.40) alloy epitaxial layers were studied through magnetic field and temperature dependent photoluminescence and time-resolved photoluminescence spectroscopy. While the linewidth and lineshape of the exciton transition for x = 0.40 indicate the presence of alloy broadening due to random anion distribution and the existence of localized exciton states, those of x = 0.13 suggest that this type of compositional disorder is absent in x = 0.13. This localization is further supported by the behavior of the exciton transitions at low temperature and high magnetic fields. InAs0.4P0.6 exhibits anomalous "S-shaped" temperature dependence of the excition emission peak below 100K as well as linewidth broadening at high magnetic fields due to the compression of the excitonic volume amid compositional fluctuations. Finally, photoluminescence decay patterns suggest that the excitons radiatively relax through two channels, a fast and a slow decay. While the lifetime of the fast decay is comparable for both compositions (similar to 30 ps), that of the slow decay increases from 206 ps to 427 ps as x increases from 0.13 to 0.40, attributable to carrier migration between the localization states of InAs0.4P0.6. (C) 2014 AIP Publishing LLC.
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    Relaxation of photoinduced spins and carriers in ferromagnetic InMnSb films
    Nontapot, K.; Kini, Rajeev N.; Gifford, A.; Merritt, T. R.; Khodaparast, Giti A.; Wojtowicz, T.; Liu, X.; Furdyna, J. K. (AIP Publishing, 2007-04)
    The authors report time resolved measurements and control of photoinduced spin and carrier relaxations in InMnSb ferromagnetic films with 2% Mn content (grown by low-temperature molecular beam epitaxy) using femtosecond laser pulses, and compare them to analogous measurements on InBeSb and InSb films. In this work, magneto-optical Kerr effect and standard pump-probe techniques provided a direct measure of the photoexcited spin and carrier lifetimes, respectively. They observe decrease in relaxations times in the high laser fluence regime and an absence of temperature dependence of the relaxation times. (c) 2007 American Institute of Physics.
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    Time-resolved differential transmission in MOVPE-grown ferromagnetic InMnAs
    Bhowmick, M.; Merritt, T. R.; Khodaparast, Giti A.; Wessels, B. W.; McGill, S. A.; Saha, D.; Pan, X.; Sanders, G. D.; Stanton, C. J. (American Physical Society, 2012-03-27)
    We measured time-resolved differential transmission in InMnAs for different pump/probe schemes as a function of temperature, laser fluence, and external magnetic field. We observed tunability of the carrier relaxation time. In addition, we found that the sign of the differential transmission changed as a function of probe wavelength. The electronic structure for InMnAs was calculated for B = 0, using an eight-band k.p model, which includes conduction and valence band mixing as well as coupling of electrons and holes to the magnetic Mn impurities. This allows us to explain some of the carrier dynamics and the sign changes in the differential transmission.