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HNPS method

The HNPS growth method is a temperature gradient method based on a direct reaction between liquid gallium (Ga) and gaseous nitrogen (N2) at high temperature (up to 1800 K) and high nitrogen pressure (up to 1 GPa).

Nitrogen molecules dissociate on the gallium surface and dissolve in the metal. Therefore, the crystals are grown from the solution of atomic nitrogen (N) in liquid gallium. The gallium nitride crystals can be grown spontaneously from the walls of the crucible, usually forming hexagonal platelets or needles. They are distributed randomly in the supersaturated zone of the solution.

For a seeded crystallization, GaN or foreign seeds have to be immersed in the gallium in the supersaturated zone of the solution. Recently, the multi-feed-seed (MFS) configuration in the HNPS growth method has been proposed and developed. This configuration was based on the conversion of free-standing HVPE-GaN crystals to free-standing, pressure grown HNPS-GaN of a much higher quality than the seeds. The great strength of this approach is that it yields several GaN crystals from one run - what’s more, the crystals satisfy all the criteria for being substrates. A few following presentations about HNPS growth of GaN allow to explain better this technology.

High Nitrogen Pressure Solution (HNPS) growth method

Method and Experimental Setup Spontaneous Crystallization

LPE Growth – Single Seed Configuration LPE Growth – The Multi Feed Seed Configuration

More articles in this field:

I. Grzegory, M. Bockowski, S. Porowski in Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials, ed. P. Capper (Wiley, New York, 2005), 173 (2005)
M. Bockowski, P. Strak, I. Grzegory, S. Porowski, in Technology of Gallium Nitride Crystal Growth ed. D. Ehrentraut, E. Meissner, M. Bockowski, (Springer, Heidelberg, 2010) 207 (2010)
I. Grzegory, M. Bockowski, P. Perlin, C. Skierbiszewski, T. Suski, M. Sarzynski, S. Krukowski and S. Porowski, in III-Nitride Semiconductors and their Modern Devices, Ed. B. Gill, Oxford Univ. Press 18 (2013) 
M. Bockowski, Japanese Journal of Applied Physics 53, 100203 (2014)
D. Ehrentraut and M. Bockowski in Handbook of Crystal Growth Second Edition: Bulk Crystal Growth: Basic Techniques, and Growth Mechanisms and Dynamics, Ed. by P. Rudolph. Elsevier 2015