ZnO thin films were epitaxially grown on α-Al2O3 (0001) substrate by radio-frequency (rf) magnetron sputtering. Among the ZnO films deposited at 550 °C, the film deposited at 80 W has the narrowest full width half maximum (FWHM) of x-ray diffraction (XRD) θ-rocking curve, 0.16°, indicating a highly c-axis oriented columnar structure. The FWHM of XRD θ-rocking curve of the ZnO film deposited at 120 W and 600 °C was 0.13° with a minimum channeling yield, 4%–5%. In photoluminescence (PL) measurement, only the sharp near band edge emission was observed at room temperature (RT). The FWHM of PL peak was decreased from 133 to 89 meV as rf power increased from 80 to 120 W at 550 °C, and that of film deposited at 120 W and 600 °C showed 76 meV which is lower value than any other ever reported. These PL results were somewhat opposite to that of XRD. From transmission electron microscopy analysis, grain size and defects were found to affect the PL properties. In this study, the PL property of undoped ZnO thin films is discussed in terms of the crystalline structure and the size of grain.

The dry etching characteristics of ZnO using an inductively couple plasma (ICP) have been investigated, for the first time, as functions of plasma chemistry, radio frequency (rf) table power, and ICP power. The CH 4 /H 2 etchant gases resulted in the highest etch rate of ZnO, suggesting that the etching of Zn in ZnO largely involves a process in which a volatile metallorganic zinc compound, such as Zn(CH 3) y is formed. The etch rate was increased with increasing rf table power, and the highest etch rate of 2000 Å/min was achieved at an rf table power of 200 W (dc bias: Ϫ80 V). As the ICP power was increased, the etch rate also increased, which suggests that the plasma density is also an important factor in this process. Furthermore, it was observed that hydrogen-containing plasma etching enhances the band-edge photoluminescence of the ZnO film.

Low-resistance and nonalloyed ohmic contacts to epitaxially grown n-ZnO were formed by exposing n-ZnO to an inductively coupled hydrogen and an argon plasma. Using Ti/Au, the specific contact resistivity of the ohmic contact was drastically decreased from 7.3×10−3 to 4.3×10−5 Ω cm2 by hydrogen plasma treatment. The photoluminescence spectrum of the hydrogen plasma treated ZnO showed a large enhancement in band-edge emission and a strong suppression in deep-level emission. These results suggest that the low contact resistivity can be attributed to an increase in carrier concentration on the ZnO surface. The specific contact resistivity of the Ar-plasma treated sample was also decreased to 5.0×10−4 Ω cm2, presumably due to the formation of shallow donor on the ZnO surface by ion bombardment.

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Copper-doped p-ZnO thin films (Cu:ZnO) were grown on α-Al 2 O 3 (0 0 0 1) and 6H:SiC(0 0 0 1) single crystal substrates by plasma-assisted molecular beam epitaxy. A p-n hetero-junction with p-Cu:ZnO/n-6H:SiC was successfully fabricated and demonstrated as a greenish-blue light emitting diode (LED). The rectifying I-V curve along with the matching photoluminescence and electroluminescence emissions characterizes the fabricated p-n hetero-junction LED. The Cu cell temperature (T Cu ) and the post-deposition annealing environment greatly influence the Cu oxidation state, and hence the electrical conversion from n-type to p-type and carrier concentration in the films. The higher T Cu and post-annealing in O-plasma were observed to be the favorable conditions for Cu 2+ and hence the p-type nature of the films.