Crystalline phase separation of InGaN layer materials prepared by metalorganic chemical vapor deposition

Zn-doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by metal organic chemical vapor deposition, and studied by a combination of high resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). HRXRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two or more InGaN bands corresponding to different x(In) for samples with phase separation. PL emissions from InGaN spread over a wider energy ranges and were modulated by the interference effects. Excitation power dependence measurements reveal 2-sets of PL emissions for samples with phase separation, but only 1-set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN-GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In-phase separation. These interesting results are correlated to the growth process and microstructural properties.