Spatially separated intrinsic emission components in InxGa1-xN ternary alloys

The characteristics of band-edge photoluminescence (PL) from Ga-rich InxGa1-xN ternary-alloy epitaxial layers with indium compositions of x=0.02, 0.03, 0.05, 0.06, and 0.09 have been comprehensively studied by means of scanning near-field optical microscopy (SNOM) in addition to conventional macroscopic PL spectroscopy. The band-edge PL from the ternary alloys consisted of two intrinsic emission components, a strong higher-energy component and a weak lower-energy component. The radiative recombination channels of the two components were not independent of each other and thermal population of carriers took place between the components. A spatial separation between the two components was clearly indicated by SNOM-PL measurements. The higher-energy component corresponded to islandlike regions with diameters of several hundred nanometers whereas the lower-energy component corresponded to dotlike regions with diameters of 50-80 nm. In addition, the regions corresponding to the lower-energy component were surrounded by a local potential maximum, which acted as a potential barrier for carriers between the higher- and the lower-energy components.