Experimental Evidence that the Plasma-assisted MBE Growth of Nitride Alloys is a Liquid Phase Epitaxy Process

摘要

In this paper we propose that under Ga-rich conditions the growth of Ill-Nitride semiconductors by plasma-assisted MBE takes place though saturation of the metallic Ga covering the surface of the growing film with nitrogen, alloy constituents and impurities. According to this model the growth process is a liquid phase epitaxy (LPE) rather than vapor phase epitaxy. Experimental evidence is presented in support of this model. Such include, for example, that the growth rate of GaN does not decrease at temperatures in excess to 800 ℃, a result attributed to higher solubility of active nitrogen in Ga at higher temperatures. Also the metallic Ga in the surface of the film controls the incorporation of impurities and is responsible for the introduction of compositional inhomogeneities and thus band structure potential fluctuations in AlGaN due to lateral statistical fluctuations of the thickness of Ga in the surface.