Improved luminescence from InGaN/GaN MQWs by reducing initial nucleation density using sputtered AlN on sapphire substrate

The edge dislocations in GaN film were reduced by lowering initial islands density and extending islands coalescence time in MOVPE, which were achieved more effectively on an ex situ sputtered AlN seed layer than on an in situ LT-GaN seed layer. GaN film with low dislocation density was achieved on an ex situ sputtered AlN seed layer by initial growth optimization as indicated by the dark spots density of 1.5 × 108 cm−2 of cathode-luminescence mapping measurement. Stress relaxation was observed for the GaN film grown from sparse initial islands on an ex situ sputtered AlN seed layer as indicated by in situ wafer curvature measurement. Temperature quenching of photoluminescence from InGaN/GaN multiple quantum wells grown on a GaN template was mitigated when an ex situ sputtered AlN seed layer was employed compared with the case with an in situ LT-GaN seed layer, confirming that the reduced nucleation density by both the use of a sputtered AlN seed and the optimization of GaN growth condition is effective for suppressing non-radiative recombination in InGaN by the reduction in edge dislocation density.