Investigations on morphology, growth mode and indium incorporation in MOCVD grown InGaN/n-GaN heterostructures

InGaN layers were grown on n-GaN/GaN/sapphire template using metal organic chemical vapor deposition system by varying Indium (In) flow rate as 11, 13 and 14 μmol/min. The nanoisland growth mode was observed by atomic force microscopy. The thickness and composition of In in the InGaN layers were determined by high resolution X-ray diffraction technique. The composition of In was found to be 15-17% depending on the In flow rate. Photoluminescence from the InGaN layers exhibit multiple peaks ranging between 479 to 657 nm, originating from the distribution of In-rich InGaN nanoislands of various sizes giving rise to localized excitons due to the In composition fluctuations. It is interesting to note that, peak emissions at 539 nm, 549 nm and 543 nm showed red and blue shift with varying In flow rate of InGaN nanoisland structures which can be attributed to the quantum confined stark effect and quantum confinement effect. Hall Effect measurement clearly indicate the variations in the semiconducting behavior of the InGaN nanoislands which influenced the composition fluctuation.