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Enhancement of Spin-Polarized Electron Emission from Strain-Compensated AlInGaAs-GaAsP Superlattices

Description: Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strain-compensated AlInGaAs/GaAsP superlattice structure is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by up to a factor 10 in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.
Date: December 8, 2006
Creator: Roberts, J.S.; U., /Sheffield; Yashin, Yu.P.; Mamaev, Yu.A.; Gerchikov, L.G.; Inst., /St. Petersburg Polytechnic et al.
Partner: UNT Libraries Government Documents Department

Improved Superlattices for Spin-Polarized Electron Sources

Description: Photoemission of polarized electrons from heterostructures based on InAlGaAs/GaAs superlattices with minimum conduction-band offsets is investigated. The comparison of the excitation energy dependence of the photoemission polarization degree with the calculated spectra makes it possible to determine the polarization losses at different stages of the photoemission. A maximum polarization of P = 91% and a quantum efficiency of QE = 0.5% are close to the best results obtained for photocathodes that are based on strained semiconductor superlattices.
Date: December 8, 2006
Creator: Mamaev, Yu.A.; Gerchikov, L.G.; Yashin, Yu.P.; Kuz-michev, V.; Vasiliev, D.; Inst., /St. Petersburg Polytechnic et al.
Partner: UNT Libraries Government Documents Department

InAlGaAs/AlGaAs Superlattices for Polarized Electron Photocathodes

Description: Highly efficient emitters of polarized electrons based on the InAlGaAs/AlGaAs superlattice give an optimistic prognosis to explorations of such structures as the sources for accelerators. A new set of these SL structures with minimized conduction band offset was designed and recently tested. A new technology of surface protection in MBE growth leads to a significantly reduced heat-cleaning temperature. At these lowered cleaning temperatures, the thermal degradation of the working structure parameters is avoided. As a result a polarization P of up to 91% at corresponding quantum efficiency (QE) of 0.3% was achieved at room temperature.
Date: August 15, 2005
Creator: Mamaev, Yu.A.; Subashiev, A.V.; Yashin, Yu.P.; Gerchikov, L.G.; Inst., /St. Petersburg Polytechnic; Maruyama, T. et al.
Partner: UNT Libraries Government Documents Department

Resonance Enhancement of Spin-Polarized Electron Emission from Strain-Compensated AlInGaAs-GaAsP Superlattices

Description: Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strain-compensated AlInGaAs/GaAsP superlattice structure is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by up to a factor 10 in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.
Date: February 21, 2006
Creator: Roberts, J.S.; U., /Sheffield; Yashin, Yu.P.; Mamaev, Yu.A.; Gerchikov, L.G.; Inst., /St. Petersburg Polytechnic et al.
Partner: UNT Libraries Government Documents Department

Comparison of ALINGAAS/GAAS Superlattice Photocathodes Having Low Conduction Band Offset

Description: The main advantage of superlattice (SL) structures as spin polarized electron emitters is the ability to provide a large splitting between the heavy hole (HH) and light hole (LH) valence bands (VB) over a large active thickness compared to single strained layers. Two important depolarization mechanisms in these structures are the scattering effects during the transit of the electrons in the active region and the depolarization that takes place in the band bending region (BBR) near the surface. In this paper, we systematically study the effects of the electron mobility and transit time by using an InAlGaAs/GaAs SL with a flat conduction band (CB). Initial results by the SPTU-SLAC collaboration using such structures grown by the Ioffe Institute showed polarization and quantum yield (QE) of 92% and 0.2% respectively. We report measurements using similar structures grown by SVT Associates. The results (polarization up to 90%) are also compared with simulations.
Date: March 31, 2006
Creator: Ioakeimidi, K,; Maruyama, T.; Clendenin, J.E.; Brachmann, A.; Garwin, E.L.; Kirby, R.E. et al.
Partner: UNT Libraries Government Documents Department