Structural and optical properties of indium-rich InGaN islands

Indium-rich In_xGa_1-xN islands ( x ≥ 0.87) grown by metalorganic chemical vapor deposition at growth temperatures ranging from 550-750°C were investigated. With the increasing growth temperature, the InGaN dot size increases while the dot density decreases due to the enhanced surface migration of In/Ga adatoms at elevated temperatures. In addition, the composition of InGaN islands was also found to be varied with the growth temperature. At lower growth temperatures, a higher Ga content can be achieved due to the relatively lower migration ability of Ga adatoms. At higher growth temperatures, the deposited InGaN material tend to decompose into In-rich islands and a thin Ga-rich layer. Photoluminescence investigations show that these In-rich islands exhibit a near-infrared emission band. For samples grown at higher temperatures, a visible emission band was also observed. The visible emission band may arise from defect bands introduced during the formation of Ga-rich InGaN layer.