Proceedings Article | 20 February 2007
Proc. SPIE. 6474, Zinc Oxide Materials and Devices II
KEYWORDS: Zinc oxide, Zinc, Lithium, Light emitting diodes, Crystals, Semiconducting wafers, Thin films, Gallium, Gallium nitride, Nanowires
We will examine a few of the outstanding new ZnO materials and device developments published in 2006. In
the area of bulk crystal growth, high-quality 3-inch ZnO wafers grown by the hydrothermal method have
become available, and Bridgman growth has also been developed. In the thin-film area, excellent ZnO layers
have been grown by liquid-phase epitaxy. Other types of epitaxial material have also shown improvements,
and the quantum Hall effect has now been observed, along with photoluminescence (PL) linewidths as low as
110 &mgr;eV. In the area of impurity characterization, radioactive-tracer methods have been used to make positive
identifications of the PL donor-bound exciton lines I8 and I9, as due to Ga and In, respectively. Our
understanding of the common impurity H has also advanced, because it is now known from both theory and
experiment that interstitial H is not stable at room temperature. The same is true of the native interstitials, ZnI and OI. New results suggest that the common H-related shallow donor is probably multibonded H
substitutional on an O site, and the ZnI-related shallow donor is probably a complex, such as ZnI-NO. In the
important area of p-type ZnO, it has been demonstrated that Li and N co-doped material has a resistivity as
low as 1 &OHgr;-cm and is stable for at least one year. Also, many groups were able to make thin-film and
nanowire or nanorod p-n junction light emitting diodes (LEDs). Another very exciting development was the
creation of an edge-emitting laser diode, from rows of n-ZnO nanocrystals on a p-GaN thin film. Electronic
devices, including transparent transistors, also made great strides, producing record field-effect mobilities.
