Inclined dislocation-pair relaxation mechanism in homoepitaxial green GaInN/GaN light-emitting diodes

Abstract

The creation of symmetrical pairs of inclined dislocations was observed in the GaInN/GaN quantum wells (QWs) of $c$-axis grown green light-emitting diodes (LEDs) on low-defect density bulk GaN substrate, but not in green LEDs on sapphire substrate with high threading dislocation (TD) density. Pairs of dislocations start within 20 nm of the same QW and incline $18\ifmmode^\circ\else\textdegree\fi{}--23\ifmmode^\circ\else\textdegree\fi{}$ toward two opposite $⟨1\overline{1}00⟩$ directions or in a $120\ifmmode^\circ\else\textdegree\fi{}$ pattern. We propose that in the absence of TDs, partial strain relaxation of the QWs drives the defect formation by removal of lattice points between the two dislocation cores. In spite of those inclined dislocation pairs, the light output power of such green LEDs on GaN is about 25% higher than in LEDs of similar wavelength on sapphire.