Extended defects in semipolar (1122) gallium nitride

Semipolar (1122 ) GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are studied by transmission electron microscopy (TEM). The layers exhibit numerous defects with different geometries in comparison to the growth along the c-axis, they are identified as mostly partial dislocations, basal and prismatic stacking faults. The dislocations density is in the order of 5x109 cm-2, the corresponding Burger vectors are b = 1/6 < 2023 >, b = 1/3 < 1010 > and a small fraction of perfect a type dislocations with b = 1/3 < 1120 > has been observed. The basal stacking fault density is in the order of 1x106 cm-1. In an attempt to reduce the defect density, SixNy interlayers have been used as nanomasks for epitaxial lateral overgrowth, our analysis shows that this leads to a quite small reduction of the defects as compared to the starting layer.