| Summary: | 碩士 === 國立中興大學 === 材料工程學系所 === 95 === The ZnO microstructures were deposited on sapphire substrates using a vertical metalorganic-chemical-vapor-deposition (MOCVD) system. At first, the effects of growth temperature on the ZnO characteristics were studied. It was found that the surface morphology of the ZnO structure changed dramatically under different growth temperatures. The ZnO morphologies were film-like, nanorod-like, nanowall-like and nanowire-like structure at 350, 450, 550, and 650℃, respectively. Then the growth mechanism of ZnO nanorods, nanowalls and nanowires were discussed. The attention has especially paid to the formation of ZnO nanowalls where it follows the formation mechanism of a self-catalyst vapor-liquid-solid method. We also tried to dope Al into the ZnO microstructure. It was found that the lattice constant c increased with increasing the Al doping concentration while the peak intensity of near band edge (NBE) emission decreased. The NBE peak of Al-doped ZnO microstructure shows blue shift to the higher energy with increasing the Al concentration, which is well known as the Burstein-Moss effect. As a result, the carrier concentration of Al-doped n-type ZnO microsructure varied from 3.08×1019 to 1.29×1020 cm-3 with the carrier mobility changed from 29.4 to 23.8 cm2/V-sec. Finally, in order to replace the conventional indium-tin oxide layer, we used the Al-doped ZnO microstructure as the transparent conducting layer for the GaN light- emitting diode (LED) applications. The GaN LEDs with an Al-doped ZnO transparent conducting layer presented a forward voltage of 3.39 V and an output power of 1.7 mW at 20 mA.
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