Structural and optical properties of semipolar (112¯2) AlGaN grown on (101¯0) sapphire by metal–organic vapor phase epitaxy

Abstract We report on the growth of semipolar ( 11 2 ¯ 2 ) AlGaN in the entire composition range on ( 10 1 ¯ 0 ) sapphire by metal–organic vapor phase epitaxy. Growth rates increase linearly with the metal–organic supply and have been realized up to 2.5 μ m / h . The Al content determined by photoluminescence and transmission measurements depends linearly on the Al/Al+Ga ratio in the gas phase. The growth rate and the Al incorporation are higher for ( 11 2 ¯ 2 ) AlGaN than for (0001) AlGaN. This is attributed to different adatom mobility and desorption. The in-plane relationship of ( 11 2 ¯ 2 ) AlGaN is [ 1 ¯ 100 ] AlGaN ∥ [ 1 2 ¯ 10 ] Sap . and [ 1 ¯ 1 ¯ 23 ] AlGaN ∥ [0001] Sap . , as typical for semipolar nitrides on m -plane sapphire. For Al contents up to 60% triangle-like structures dominate the surface. For Al contents above 70% it transforms into an undulation along [ 1 ¯ 100 ] and additional dot-like structures. The smoothest surface morphologies with a rms roughnesses of 2 nm were achieved for Al mole fractions of ∼ 50 % .