Pseudohalide vapour growth of thick GaN layers

Abstract

The synthesis and growth of crystalline GaN from elemental gallium and ammonia as feeding materials has been investigated. Experimental observations lead to the suggestion that the presence of carbon drastically changes the chemistry of the GaN formation. It is supposed that graphite parts react with ammonia yielding the pseudohalide hydrogen cyanide, HCN. This acts as a transporting agent for Ga, forming volatile Ga(CN) ( g) . Crystalline GaN is deposited either by the thermal decomposition of gallium monocyanide or by a reaction that is completely analogous to that of the common HVPE growth technique with the only difference that HCl is replaced by HCN. The different chemical reactions involved in this “pseudohalide vapour phase epitaxy” (PVPE) process are considered from a thermodynamic point of view. The potential of the PVPE as a disputable alternative method for the growth of bulk GaN crystals is still to be investigated.