Growth and characterisation of semi-polar (1l2¯2) InGaN/GaN MQW structures

Semi-polar (1l2¯2) GaN films have been grown by organometallic vapour-phase epitaxy (OMVPE) on m  -plane (1l¯00) sapphire. The in-plane orientation of the GaN with respect to the sapphire substrate was determined to be [1l¯00]GaN∥[1l2¯0]sapphire and the projections of [0 0 0 1]GaN and [1l2¯0]GaN∥[0 0 0 1]sapphire. The smooth planar films displayed a distinct in-plane anisotropic mosaicity with the symmetric (1l2¯2) reflection along the GaN m-direction (XRD ω FWHM of 1080 arcsec) broader than that along the projected c-direction (665 arcsec). TEM analysis indicated the presence of line defects threading through the layer but few stacking faults. Two semi-polar (1l2¯2) InGaN/GaN 10-period quantum well structures with wells thicknesses (alloy compositions) of 3.4 nm (12%) and 3.9 nm (19%) showed strong photoluminescence peaks at 430 and 500 nm, respectively.