Morphological evolution of InGaN/GaN quantum-well heterostructures grown by metalorganic chemical vapor deposition

Abstract

The morphological evolution of InGaN/GaN multiple-quantum wells (MQWs) grown by metalorganic chemical vapor deposition has been examined by atomic force microscopy and cross-sectional transmission electron microscopy. We have determined that GaN barrier growth at low temperature (∼800 °C) in a H2-free environment results in a microstructure that consists of not only V-defects, but also inclusions embedded within V-defects that originate at the first InGaN-to-GaN growth interface. Propagation of the inclusions results in progressive deterioration of the surface morphology and reduced MQW thermal stability as quantum-well periods are added. Raising the GaN barrier growth temperature to 900 °C or adding H2 suppresses inclusion propagation entirely and preserves two-dimensional step-flow growth mode, resulting in superior morphology and higher thermal stability.