V-defects formation and optical properties of InGaN/GaN multiple quantum well LED grown on patterned sapphire substrate

To enhance light extraction efficiency, high-quality InGaN/GaN multiple quantum well (MQW) LED was grown on cone-shaped patterned sapphire substrate (CPSS) by using metal organic chemical vapor deposition (MOCVD). In the growth of InGaN multiple quantum well structure, all V-defects are not always connected with threading dislocations (TDs) at their bottom, also many V-defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation. The formation of the V-defect is kinetically controlled by reduced Ga incorporation on the pyramid walls ({101¯1} planes). The improvement of luminous intensity and reverse I–V   characteristic (the leakage currents of the LEDs grown on CPSS and USS were −0.23μA and −0.76μA, respectively, at the reverse voltage of −10 V) was explained by considering not only an increase of the extraction efficiency via the suppressed total internal reflection at the CPSS interface but also a decrease of V-defect density.