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

We report on the growth of semipolar (112¯2) AlGaN in the entire composition range on (101¯0) sapphire by metal–organic vapor phase epitaxy. Growth rates increase linearly with the metal–organic supply and have been realized up to 2.5μm/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 (112¯2) AlGaN than for (0001) AlGaN. This is attributed to different adatom mobility and desorption. The in-plane relationship of (112¯2) AlGaN is [1¯100]AlGaN∥[12¯10]Sap. and [1¯1¯23]AlGaN∥ [0001]Sap.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%∼50%.

► MOVPE growth of semipolar (11–22) AlGaN in entire composition range.
► Structural and optical properties were determined by several methods.
► The (11–22) crystal orientation could be isolated through variation of V/III ratio.
► Smooth and crack free surfaces were achieved for Al mole fractions of ∼50%∼50%.
► Aluminium incorporation and growth rates are higher for semipolar than for polar AlGaN