Improvement of emission efficiency with a sputtered AlN buffer layer in GaInN-based green light-emitting diodes

Abstract

We examined a sputtered AlN (sp-AlN) buffer layer to improve the emission efficiency of GaInN-based green LEDs. Both the electroluminescence and photoluminescence emission efficiencies are improved in a LED with a sp-AlN buffer layer compared to that with a conventional low-temperature GaN buffer layer. To identify the origin of the improvements, we carried out the analysis including X-ray diffraction, surface morphology, initial nucleation growth, and temperature-dependent PL. Through analysis and consideration, we showed that the improvements are mainly caused by less strain and a lower degree of carrier localization in quantum wells (QWs), that is highly influenced by the grain diameter of the GaN island at initial growth. These results indicate that a sp-AlN buffer layer induces less compositional pulling that results in less strain and alloy fluctuation in QWs, simultaneously.