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InGaN layers were grown simultaneously on (112¯2) GaN and (0001) GaN templates by metalorganic vapour phase epitaxy. At higher growth temperature (≥750 °C), the indium content (<15%) of the (112¯2) and (0001) InGaN layers was similar. However, for temperatures less than 750 °C, the indium content of the (112¯2) InGaN layers (15%–26%) were generally lower than those with (0001) orientation (15%–32%). The compositional deviation was attributed to the different strain relaxations between the (112¯2) and (0001) InGaN layers. Room temperature photoluminescence measurements of the (112¯2) InGaN layers showed an emission wavelength that shifts gradually from 380 nm to 580 nm with decreasing growth temperature (or increasing indium composition). The peak emission wavelength of the (112¯2) InGaN layers with an indium content of more than 10% blue-shifted a constant value of ≈(50–60) nm when using higher excitation power densities. This blue-shift was attributed to band filling effects in the layers.

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)

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