Improvements in internal quantum efficiency and wavelength stability of InGaN orange and red MQWs grown on a semi-polar plane.

Abstract

An innovative epitaxial technology was adopted to directly grow semi-polar orange and red InGaN/GaN MQWs on common sapphire substrate. Our research results show that InGaN/GaN MQWs grown on the semipolar surface have significant improvements in internal quantum efficiency (IQE) and color stability compared to those grown on the polar surface. For polar c-plane red MQWs: Strong compressive strain and quantum-confined Stark effect (QCSE) induce pronounced band bending, as evidenced by strain gradients in TEM cross-sections. In-rich clusters form at the QW center due to In migration, causing localized strain concentration and interface blurring. For semi-polar red QWs:reduced polarization fields result in uniform in-plane strain distribution, with significant strain relaxation near QW edges.TEM analysis confirms suppressed QCSE and homogeneous In incorporation, minimizing spectral broadening. As the laser excitation power changes, the peak wavelength blue shift of polar c-plane red MQWs was 63 nm, at peak wavelength of 675 nm and 612.1 nm, the corresponding IQE is 4.4% and 10.8% respectively. While the peak wavelength blue shift of semi-polar plane red MQWs was 19 nm, at peak wavelength of 607 nm and 588 nm, the corresponding IQE is 22.2% and 35.6% respectively.