The creation of symmetrical pairs of inclined dislocations was observed in the GaInN/GaN quantum wells of c-axis grown green light-emitting diodes on low-defect density bulk GaN substrate, but not in green LEDs on sapphire substrate with high threading dislocation density. Pairs of dislocations started within 20nm of the same quantum wells and inclined 18°–23° toward two opposite <1¯1•0> directions or in a 120° pattern. It was proposed that, in the absence of threading dislocations, partial strain relaxation of the quantum wells drove defect formation by the removal of lattice points between the two dislocation cores. In spite of the inclined dislocation pairs, the light output power of such green LEDs on GaN was about 25% higher than in LEDs of similar wavelength on sapphire.

Inclined Dislocation-Pair Relaxation Mechanism in Homoepitaxial Green GaInN/GaN Light-Emitting Diodes. M.Zhu, S.You, T.Detchprohm, T.Paskova, E.A.Preble, D.Hanser, C.Wetzel: Physical Review B, 2010, 81[12], 125325