Isolated red quantum wells with strain relaxation induced by V-pits and trench structures

Abstract

Carrier localization leads to efficient emission in InGaN/GaN multi-quantum wells (MQWs), especially in the long-wavelength range. Nanostructures in MQWs can facilitate the formation of carrier localization centers. In this work, high-density V-pits and trench structures were introduced in MQWs by constant low-temperature growth. Isolated red MQWs were achieved due to the carrier blocking effect caused by the V-pits and trench structures. Meanwhile, the V-pits and trench structures caused significant stress relaxation in MQWs. The topmost quantum wells (QWs) achieved red emissions due to the composition-pulling effect, while the bottom QWs exhibited green emissions. In electroluminescence measurement, a single red emission peak appeared at 636 nm at 0.1 A/cm2. Temperature-dependent photoluminescence (PL) results showed that the PL integral intensity of the red MQWs at room temperature is about 11.32% of that at 6 K, while that of the green MQWs is only 0.09%. The PL lifetime for red emissions was more than 20 times longer than that for green ones. This study presents a new method to achieve carrier localization in red MQWs to minimize defect-related effects.