InGaN quantum well epilayers morphological evolution under a wide range of MOCVD growth parameter sets

This study exemplifies the use of TappingModeTM atomic force microscopy (AFM) surface morphology imaging to investigate and optimise the metalorganic chemical vapour deposition (MOCVD) growth conditions and post-growth stability of thin (<40 A) InGaN layers with direct implications to the structural and optical properties of blue (460 nm) and green (520 nm) LEDs. InGaN epilayers less than 40 A thick of ∼20% solid phase indium were produced on thick (3-4 µm) 2″ GaN templates grown on (0001) c -plane sapphire substrates. The morphological evolution of the InGaN material was studied utilising a DI3100 AFM tool. Surface morphology and its correlation with photoluminescence and X-ray diffraction results will be discussed for every set of conditions employed. More specifically, the post-growth ambient exposure and thermal stability of the uncapped InGaN epilayers were investigated. In addition, the initial stage of subsequent GaN growth, which is an essential step towards the manufacture of LED active regions, was examined. Based on the above findings, a flexible MOCVD growth parameter space and improved LED constituent layer sequencing techniques have been established leading to more efficient and stable LED devices. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)