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We investigated the response of wurzite GaN thin films to energetic ion irradiation. Both swift heavy ions (92 MeV Xe 23+ , 23 MeV I 6+ ) and highly charged ions (100 keV Xe 40+ ) were used. After irradiation, the samples were investigated using atomic force microscopy, grazing incidence small angle X-ray scattering, Rutherford backscattering spectroscopy in channelling orientation and time of flight elastic recoil detection analysis. Only grazing incidence swift heavy ion irradiation induced changes on the surface of the GaN, when the appearance of nanoholes is accompanied by a notable loss of nitrogen. The results are discussed in the framework of the thermal spike model.

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In this article, the growth and coalescence of semi‐polar false(11true2‾2false) oriented GaN layers, deposited on pre‐structured r‐plane sapphire substrates, is studied with the help of Si‐doped marker layers. It has been found to be very important to adjust the shape of the initial GaN stripes by varying the growth temperature to obtain not only a smooth surface, but also a small density of basal plane stacking faults (BSFs) and threading dislocations (TDs) on the wafer surface. With the help of transmission electron microscopy (TEM) and cathodoluminescence measurements (CL), we can conclude that during growth, we need to achieve a compromise between small BSF density, small TD density, and perfect coalescence with smooth surface, free of fissures, and other growth artifacts. Also the formation of arrow‐head‐shaped surface artifacts called “chevrons” can be understood to be caused by imperfect coalescence. We observe with the help of the marker layers that the growth rate fluctuates between neighboring stripes. This effect strongly increases for higher growth temperature.

In this article two methods for improvements of (11$ \bar 2 $2) oriented semipolar GaN grown by MOVPE on prestructured sapphire substrates are investigated. The integration of a SiNx interlayer helps to obtain a better crystal quality. Also the overgrowth of the MOVPE samples by HVPE is a way to obtain a smoother GaN surface. A high incorporation of oxygen on (11‐22) oriented GaN compared to (0001) oriented GaN grown by HVPE was observed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)