Browsing by Author "Chang, K. J."

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Growth of gamma-In2Se3 films on Si substrates by metal-organic chemical vapor deposition with different temperatures
(2008-04-01)
Huang, Yen-Chin
;
Li, Zhen-Yu
;
Uen, Wu-Yih
;
Lan, Shan-Ming
;
Chang, K. J.
In2Se3 films were deposited on the p(+)-Si(1 1 1) substrates by metal-organic chemical vapor deposition (MOCVD) for the first time at temperatures higher than 500 degrees C. Trimethyl indium (TMI) and H2Se were used as the source reactants with the flow ratio of [H2Se]/[TMI] being maintained at 6.7. The growth temperature was varied from 350 to 650 degrees C. Powder X-ray diffraction analyses revealed that the In2Se3 film grown is polycrystalline and has a wurtzite structure when the growth temperature is below 450 degrees C. Instead, a rhombohedral structure began to appear when the growth temperature is above 450 degrees C. Besides, SEM observations indicated a surface morphology of columnar structure for all films grown. Optical properties were examined by photoluminescence (PL) measurements. It was found that by conducting the growth at 550 degrees C a strong PL emission at around 2.14 eV was observed at 20 K. The luminescence mechanism was found to be dominated by the free excitons based on the temperature-dependent PL spectra from 20 to 120 K. However, bound exciton emissions were also observed or even became the dominant band when the films were grown at temperatures lower than 500 degrees C. Otherwise, the intensity of the 2.14 eV peak reduced greatly when the growth temperature was higher than 5 50 degrees C. Power-dependent PL measurements with excitation power varying from 0.1 to 100 mW confirm the luminescent mechanism and the material quality of the film grown at 550 degrees C. It is concluded that single-phase gamma-In2Se3 films can be achieved at temperatures lower than 450 degrees C; however, good-quality In2Se3 films with the simultaneous appearance of gamma- and beta-phase structures can be grown at around 550 degrees C. (C) 2007 Elsevier B.V. All rights reserved.
In0.11Ga0.89N-based p-i-n photodetector
(2009)
Su, Y. K.
;
Lee, H. C.
;
Lin, J. C.
;
Huang, K. C.
;
Lin, W. J.
The InGaN photodetector with a In composition of i-In0.11Ga0.89N active layer have been fabricated by MOCVD system. From the photoluminescence measurement, the FWHM of InGaN epitaxial layer was only 13.8 nm. The strong luminescence peak was located at wavelength of 399 nm. We also found that the FWHM of X-ray diffraction of GaN and InGan layer were 218 and 350 arcsec, respectively. Clear photo-responses are also observed in InGaN photodetector with 11% content at responsivity measurement. The cut-off range of spectral responsivity was occurred at 400 nm. The highest spectral responsivity of photodetector was 0.206 A/W at wavelength of 380 nm. The rejection ratio was approached to 103. The external quantum efficiency was about 67%. The current density-voltage (J-V) characteristic of i-InGaN p-i-n photodetector was measured. The dark and photo current density were 1.77x10(-4) A/cm(2) and 4.5x10(-2) A/cm(2) when biased at -3 V, respectively. At photovoltaic characteristics, the V-oc and J(sc) of the i-InGaN photodetector are 1.63 V and 3.1x10(-2) A/cm(2), respectively. The fill factor of i-InGaN p-i-n photodetector was about 37%. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Morphology and optical properties of zinc oxide thin films grown on Si (100) by metal-organic chemical vapor deposition
(2009-01-01)
Lan, S. M.
;
Uen, W. Y.
;
Chan, C. E.
;
Chang, K. J.
;
Hung, S. C.
Undoped zinc oxide (ZnO) thin films were deposited on Si (100) substrates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD). After a nucleation layer of ZnO about 500 A... was deposited, top ZnO films with 320-440 nm in thickness were fabricated at temperatures varying from 450 to 600 A degrees C, respectively. X-ray diffraction analyses demonstrate that all the films grown have polycrystalline wurtzite structure. Scanning electron microscopy observations indicate that ZnO films grow with c-axis aligned grains when the deposition temperature is lower than 600 A degrees C. However, 3D microstructures without c-axis alignment were found when the film was deposited at 600 A degrees C. Room temperature photoluminescence (PL) spectra peaking at 3.27-3.29 eV were observed for the ZnO films grown at 450-600 A degrees C. However, only the spectrum from the film grown at 600 A degrees C could present a high intensity ratio of the ultraviolet band to deep-level emissions, which is above 392 and show a minimum full-width at half-maximum of 99 meV for the ultraviolet band. Temperature-dependent PL measurements from 20 to 300 K exhibited the luminescent mechanism of the present ZnO films to be near band excitonic emission.