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ZnO‐based compounds that exhibit a number of strongly overlapping emission bands in visible spectral region are promising materials for white‐light emitters with continuous emission spectrum. Defect‐related emission in doped with different impurities ZnO, however, spreads from green to red spectral region, so its shift toward shorter wavelengths is required. We supposed that this problem can be solved due to broadening of ZnO band gap by alloying ZnO with MgO. The enhancement of visible emission brightness is also an important problem. In this work, MgxZn1‐xO ceramics with x =0 and x=0.2 were sintered both in air and Zn vapor at 950 oC. Emission and Raman scattering spectra were measured at 300 K using 325 nm line of He‐Cd laser as excitation source. In samples sintered in air, bright UV emission and weak visible one took place, adding MgO to ZnO resulting in blue‐shift of the latter. Sintering in Zn vapor was found to weaken UV emission and to increase drastically the brightness of visible one especially in blue‐green spectral region. As a result, bright blue radiation was observed from MgZnO ceramics under excitation by considerably week UV light. Obtained effects were accounted for by the shift of “green” centers energetic level with respect to involved band edge as a result of band‐gap broadening and by the increase of this center density due to annealing in Zn vapor. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Confocal micro-Raman spectroscopy was applied to study the cleaved surface of vertical GaN Gunn-diode structure grown by molecular-beam epitaxy. The analysis of lateral scanning along the cleaved edge reveals the depth profile of elastic strain, quality of the crystal structure, and the concentration of charge carriers. Results are compared with that of axial confocal Raman depth profiling normal to the structure's surface. Decrease of compressive strain near the cleaved edge in the direction from the substrate to the structure's surface and in the growth plane towards the cleaved edge is shown. The decrease in charge carrier concentration in the undoped n 0 -GaN channel region in comparison with the n + -GaN contact region is identified. Peculiarities of the resulting spatial profiles of free charge carriers and their correlation with the initial doping profile are discussed.