Epitaxial Lateral Overgrowth of Nitrogen-Polar (0001) GaN by Metalorganic Chemical Vapor Deposition

Epitaxial lateral overgrowth (ELO) of nitrogen-polar (0001̅) GaN (N-polar GaN) by metalorganic vapor deposition has been studied to achieve a high microstructural quality of N-polar GaN. The influence of growth conditions on lateral growth is investigated, and a correlation of growth conditions with the observed inversion of polarity is established. Most of the observed trends for N-polar ELO are contrary to those reported for Ga-polar experiments. Such differences are explained by considering the property of surface reactivity of N-polar GaN with hydrogen species. On the basis of the trends of the occurrence (or absence) of polarity inversion, an atomistic model is proposed to explain the origin of polarity inversion. This model also allows us to control the process and to completely eliminate polarity inversion, resulting in fully coalesced, purely N-polar GaN with improved crystalline quality.