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    Electroreflectance and photocurrent measurement of ZnSe/Alq 3/TPD heterostructure on Si-substrate
    (2005-11-20) ;
    Keawprajak, A.
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    The optical transition energy in ZnSe/tris(8-hydroxyquinoline) aluminum (Alq<inf>3</inf>)/N,N′-bis(3-methylphenyl)-N,N′-diphenyl-benzidine (TPD) heterostructure were investigated by room-temperature electroreflectance (ER) and photocurrent (PC) measurements. PC signal showed wavelength response of the device in the range of 450-1100 nm. ER features due to optical transition energy of the single quantum well of this structure were observed. The transition energies were determined by fitting the ER spectra to the theoretical line-shape expression. The subband transition energy decreased with increasing well thickness. Under applied voltage, both ER signals show significant shift due to the quantum confined Stark effect. © 2005 Elsevier B.V. All rights reserved.
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    Electroreflectance study of antimony doped ZnO thin films grown by pulsed laser deposition
    (2021-10-01)
    Jessadaluk, Sukittaya
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    Rattanawarinchai, Prapakorn
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    In this research, antimony doped ZnO (SZO) thin films with various doping content have been grown on a c-Al<inf>2</inf>O<inf>3</inf> substrate by pulsed laser deposition. The effect of the applied electric field on the bandgap of SZO thin films was studied by electroreflectance (ER) spectroscopy using a capacitor-type geometry. Hall effect measurements indicate that the p-type conductivity of SZO is realized for the Sb<inf>2</inf>O<inf>3</inf> weight percentage at 2%. The blue shift of the energy bandgap was observed in thin films after increasing the doping concentration. The Burstein-Moss effect is the crucial mechanism for the blue shift of the SZO bandgap. Furthermore, we found the red shift of bandgap in all samples, which was measured under various electric fields by ER spectroscopy. The changes of the optical transition in the band structure should be the origin of the red shift behaviors of the SZO bandgap under the presence of the electric field. Based on our results, we can design and optimize the bandgap of SZO for optoelectronic devices.