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

Semi-polar ( 1 l 2 ¯ 2 ) GaN films have been grown by organometallic vapour-phase epitaxy (OMVPE) on m-plane ( 1 l ¯ 0 0 ) sapphire. The in-plane orientation of the GaN with respect to the sapphire substrate was determined to be [ 1 l ¯ 0 0 ] GaN∥[ 1 l 2 ¯ 0 ] sapphire and the projections of [0 0 0 1] GaN and [ 1 l 2 ¯ 0 ] GaN∥[0 0 0 1] sapphire. The smooth planar films displayed a distinct in-plane anisotropic mosaicity with the symmetric ( 1 l 2 ¯ 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 ( 1 l 2 ¯ 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.