Browsing by Author "Kuo, Chin-Chia"

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Growth and Characteristics of a-Plane GaN on ZnO Heterostructure
(2012)
Huang, Huei-Min
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Kuo, Chin-Chia
;
Chang, Chiao-Yun
;
Lin, Yuan-Ting
;
Lu, Tien-Chang
We report on growth and characteristics of a-plane GaN/ZnO/GaN epitaxial structures, which can be applied to various optoelectronic devices. The unique optical transitions intrinsic to heterovalent interfaces were found and analyzed. Clear carrier localization effect in the GaN/ZnO heterointerface is observed from the S-shaped energy shift with increasing temperature in the temperature-dependent photoluminescence measurement. The carrier localization also results in strong luminescent intensity and dominates the emission spectrum at room temperature. In addition, the acceptor level originated from the Zn out-diffusion from the ZnO layer is observed in the low temperature photoluminescence spectra, and its binding energy is estimated to be about 0.311 eV. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.080203jes] All rights reserved.
The effect of thermal annealing on the optical and electrical properties of ZnO epitaxial films grown on n-GaAs (001)
(2015-01-01)
Liu, Wei-Rein
;
Lin, Bi-Hsuan
;
Lin, Chi-Yuan
;
Yang, Song
;
Kuo, Chin-Chia
Wurtzite ZnO epitaxial layers grown on n-type GaAs (001) by pulsed laser deposition (PLD) exhibited n-type conductivity. Post-growth annealing leads the conversion of carrier type from electron to hole, as revealed by Hall effect measurements, although only moderate structural improvement was observed. The carrier type conversion is attributed to thermally activated arsenic diffusion from the substrate, confirmed by secondary ion mass spectrometry and photoluminescence. The surface electrical properties of both the as-deposited n-type and annealed p-type ZnO epitaxial layers were thoroughly characterized by Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The results indicated the existence of a high density of surface states close to the ZnO midgap with a density of a few 10(14) cm(-2) eV(-1). The Fermi levels (E-F) of n- and p-type ZnO epitaxial layers were found to be 1.06 eV below the conduction-band minimum (CBM) and 1.612-1.769 eV above the valence-band maximum (VBM), respectively. The small EF difference between the n- and p-type ZnO epitaxial layers implies Fermi level pinning at the surface of both n-and p-type ZnO epitaxial layers.