Phase separation in thick InGaN layers – A quantitative, nanoscale study by pulsed laser atom probe tomography

Pulsed laser atom probe tomography was employed to study 300 nm thick In0.25Ga0.75N layers grown on a GaN buffer layer. The unique three-dimensional data provided by atom probe tomography revealed a complex microstructure in the InGaN formed by indium-rich columns and plates adjacent to strongly indium-depleted regions. This complex indium-related domain structure is likely to represent the early stages of spinodal decomposition occurring during layer growth. The interface with the buffer layer is characterized by the absence of this microstructure and a generally more homogeneous indium distribution. Also, a significantly reduced InN mole fraction was found in that region. Both are believed to be a result of the interfacial misfit strain, which suppresses phase separation and impedes indium incorporation during growth, which is termed the compositional pulling effect.