New Developments in ZnO Materials and Devices
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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 μeV. 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 Ω-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.
Look, D. C.
(2007). New Developments in ZnO Materials and Devices. Proceedings of SPIE, 6474, 647402.