This article presents some investigation results of GaN hexagonal crystals deposited on Si pyramids as field emitters. GaN is considered to be an interesting material for field emission cathodes due to its stability. This exceptional stability makes emitter shaping difficult work. Si is easily formed but GaN grown on Si substrate forms small, separate grains. The formation of such single crystals on Si pyramids may be an easy way for field emitter array formation. The obtained results show that this approach may be useful in practical application. There are some indications that the overheating of emitter tips may lead to decomposition of GaN and to release of metallic Ga.