Cover Picture: phys. stat. sol. (a) 205/7

The cover picture illustrates electroluminescence results for nonpolar a ‐plane 360 nm UV LEDs grown over high quality SLEO templates reported by Bilge Imer et al. (p. 1705): To overcome the obstacle of high defect densities in these devices, nonpolar a ‐plane GaN films were grown by sidewall lateral epitaxial overgrowth (SLEO) technique with a threading dislocation density of ∼10 6 –10 7 cm –2 . The device structure is depicted at the upper right. For comparison, 360 nm GaN/AlGaN multiple quantum well ultraviolet light emitting diodes were grown over planar a ‐plane films and reduced defect density SLEO films with metalorganic chemical vapor deposition and processed together. The photographs illustrate the emission of SLEO a ‐plane on wafer LEDs under the microscope. Compared with the defected planar films, the high quality SLEO material yielded ∼100–300 times higher external quantum efficiency and ∼2.5–3 times lower series resistance with an electroluminescence peak at 360 nm (lower left). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)