Vertical cavity surface emitting laser action of an all monolithic ZnO-based microcavity

We report on room temperature laser action of an all monolithic ZnO-based vertical cavity surface emitting laser (VCSEL) under optical pumping. The VCSEL structure consists of a 2{\lambda} microcavity containing 8 ZnO/Zn(0.92)Mg(0.08)O quantum wells embedded in epitaxially grown Zn(0.92)Mg(0.08)O/Zn(0.65)Mg(0.35)O distributed Bragg reflectors (DBRs). As a prerequisite, design and growth of high reflectivity DBRs based on ZnO and (Zn,Mg)O for optical devices operating in the ultraviolet and blue-green spectral range are discussed.Comment: Copyright (2011) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Appl. Phys. Lett. 98, 011101 (2011) and may be found at http://apl.aip.org/resource/1/applab/v98/i1/p011101_s

Electronic structure of the muonium center as a shallow donor in ZnO

The electronic structure and the location of muonium centers (Mu) in single-crystalline ZnO were determined for the first time. Two species of Mu centers with extremely small hyperfine parameters have been observed below 40 K. Both Mu centers have an axial-symmetric hyperfine structure along with a [0001] axis, indicating that they are located at the AB_{O,//} and BC_{//} sites. It is inferred from their small ionization energy (~6 meV and 50 meV) and hyperfine parameters (~10^{-4} times the vacuum value) that these centers behave as shallow donors, strongly suggesting that hydrogen is one of the primary origins of n type conductivity in as-grown ZnO.Comment: 4 pages, 4 figures, submitted to PR