Some nice Raman and other optical spectroscopy results for GaN films grown at only 200 C with a plasma assisted ALD system converted to use with one of our hollow cathode plasma sources. The results have recently been published in. J. Vac. Sci. Technol. A 37 (2019) 050901 by Nese Gungor and Mustafa Alevli of Marmara University in Turkey. There are some impressively narrow phonon line widths for GaN grown at that temperature. This is the 28th paper we are aware of on ALD using hollow cathode plasma sources, and this paper continues to demonstrate the dominance in the low temperature growth of GaN by the Turkish groups making use of hollow cathode technology.
The main advantage of the hollow cathode plasma sources has been the reduction of oxygen contamination from the source itself. The attached image shows a quartz ICP source etched through over a period of some years by plasma etching. This source of oxygen contamination has been known since at least 1989 and is discussed in our company white paper “Oxygen Contamination in PE-ALD“. However, the hollow cathode sources are also high radical density plasma sources with many other lesser known advantages (see “Hollow Cathode Plasma Sources for Plasma Enhanced ALD and PECVD“).