The NL-3 Laboratory specializes in crystal growth research with the use of high temperature systems with gas pressure range up to 2 GPa and temperature up to 2000 K.
With over 30-year-long tradition in research it succeeded in developing many important methods of crystal growth. The influence of high pressure on the properties of systems containing semiconductors and superconductors were studied by annealing, crystallization and Differential Thermal Analysis (DTA) experiments, allowing the determination of the character of phase diagrams of III - V nitrides (GaP-GaN), NbN, MoN, and II-VI compounds (HgS, HgTe, HgSe). One of the most important results was the evaluation of the equilibrium curve for a Ga-GaN-N2 system [1].
In the early 1990s, due to an extreme importance of gallium nitride, the main effort was put into the optimization of this material for short wavelength optoelectronics applications. The growth of GaN crystals from solution of atomic nitrogen in liquid gallium under high nitrogen pressure (High Nitrogen Pressure Solution growth; HNPS method) resulted in the highest quality material (hexagonal GaN platelets grown in a spontaneous way) with dislocation density as low as 102 cm-2 [2].
In 2003 work on the Hydride Vapor Phase Epitaxy (HVPE) of GaN was started in the Laboratory. The motivation was to increase the size of the pressure grown crystals and crystallize seeds for the HNPS growth. Two-inch and up to 1 mm thick free standing HVPE-GaN crystals were obtained using MOCVD-GaN/sapphire templates. Recently a Multi Feed Seed (MFS) configuration in the HNPS growth method has been proposed and developed. This configuration is 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 [3].
In 2012 the Laboratory started to collaborate with Ammono S.A. and use the ammonothermally grown GaN crystals (Am-GaN) as seeds for the HVPE growth. Crack-free and up to 2.5 mm thick HVPE-GaN layers were obtained. The free-standing HVPE-GaN crystals sliced from Am-GaN seeds showed high structural as well as optical, electrical and thermal qualities [4].
