Long wavelength red to green emissions from {11 2¯ 2} semipolar multi-quantum wells on fully relaxed InGaN underlayer

In this study, we present {11 2 ¯ 2} InGaN underlayers of high In composition and multi-quantum wells (MQWs) grown using the m-plane sapphire substrate. Fully relaxed InGaN templates with high In composition (In: ∼18%) were investigated. We used an InGaN template with an In composition of 16.5%. The photoluminescence (PL) spectrum of MQWs on the InGaN template exhibited higher emission intensity and longer emission wavelength than that on a GaN template. Moreover, an InGaN barrier was found to be more suitable than a GaN barrier for the long-wavelength (red) region in the InGaN underlayer. The intensity of the PL spectrum of InGaN/InGaN MQWs was twice as high as that of InGaN/GaN MQWs in the red emission region. Finally, we analyzed the optical polarization of the MQWs on {11 2 ¯ 2} InGaN underlayers and its characteristics were discussed using theoretical equations.