Browsing by Author "Chen, Jian-Wen"

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Characterizations of Ga-doped ZnO films on Si (111) prepared by atmospheric pressure metal-organic chemical vapor deposition
(2009-11-01)
Huang, Yen-Chin
;
Li, Zhen-Yu
;
Weng, Li-Wei
;
Uen, Wu-Yih
;
Lan, Shan-Ming
Gallium-doped ZnO films were grown on p-Si(111) substrates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using diethylzinc and water as reactant gases and triethyl gallium (TEG) as a n-type dopant gas. The structural, electrical, and optical properties of ZnO:Ga films obtained by varying the flow rate of TEG from 0.56 to 3.35 mu mol/min were examined. X-ray diffraction patterns and scanning electron microscopy images indicated that Ga doping plays a role in forming microstructures in ZnO films. A flat surface with a predominant orientation (101) was obtained for the ZnO:Ga film fabricated at a flow rate of TEG = 2.79 mu mol/min. This film also revealed a lowest resistivity of 4.54 x 10(-4) Omega cm, as measured using the van der Pauw method. Moreover, low temperature photoluminescence (PL) emission recorded at 12 K demonstrated the Burstein Moss shift of PL line from 3.365 to 3.403 eV and a line broadening from 100 to 165 meV as the TEG flow rate varied from 0.56 to 2.79 mu mol/min. This blueshift behavior of PL spectra from ZnO: Ga films features the degeneracy of semiconductor, which helps to recognize the enhancing of transparency and conductivity of ZnO films fabricated by AP-MOCVD using Ga-doping technique. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3212895]
Intrinsic p-type ZnO films fabricated by atmospheric pressure metal organic chemical vapor deposition
(2010-11-01)
Huang, Yen-Chin
;
Li, Zhen-Yu
;
Weng, Li-Wei
;
Uen, Wu-Yih
;
Lan, Shan-Ming
The structural, electrical, and optical properties of ZnO films fabricated by atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) under various gas flow ratios of [H(2)O]/[DEZn] (VI/II ratio) ranging from 0.55 to 2.74 were systematically examined. Hall effect measurements exhibited an evident effect of the VI/II ratio on the conduction type of the intrinsic films. An n-type film was fabricated at the VI/II ratio=0.55; however, p-type ZnO films with the hole concentration of the order of 10(17) cm(-3) could be achieved at VI/II ratios higher than 1.0. In particular, the highest mobility of 91.6 cm(2)/V s and the lowest resistivity of 0.369 Omega cm have been achieved for the specimen fabricated at the VI/II ratio=1.10. Moreover, room-temperature photoluminescence (PL) measurements demonstrated an interstitial Zn (Zn(i)) donor defect related emission at 2.9 eV for the n-type film, while a Zn vacancy (V(Zn)) acceptor defect related one at 3.09 eV for the p-type films. The existence of material intrinsic defects was further confirmed by low temperature PL measurements conducted at 10 K. Conclusively, the conduction type of undoped ZnO films deposited by AP-MOCVD is resolved by the VI/II ratio used, which causes the formation of various kinds of intrinsic defects, Zn(i) otherwise VZn. p-type ZnO films with the hole concentration in the range of (1.5-3.3) x 10(17) cm(-3) can be achieved with good reproducibility by modulating a VI/II ratio the range 1.0-2.2 for the AP-MOCVD process. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3484138]