Abstract: Described is a horizontal reactor for processing GaN based semiconductors which achieves high quality epitaxial growth because no dust is produced through use of a ferrofluidic power transmission or gas flow to rotate its susceptor, elements from thermal decomposition of ammonia gas are provided separately at high temperatures at a position proximate the substrate so that premature reaction between ammonia ions and the reactant gases is avoided, and the reactor is constructed to suppress thermal convection attributed to heat from the susceptor which otherwise hinders smooth epitaxial growth.