Effects of off-axis GaN substrates on optical properties of m-plane InGaN/GaN light-emitting diodes

Effects of off-axis substrates on m-plane InGaN/GaN light-emitting diodes (LEDs) grown by metal organic chemical vapor deposition were investigated. The surface morphology of n-GaN was improved by increasing an off-axis angle from the m-plane toward the c-plane. The InGaN/GaN quantum wells (QWs) grown on the off-axis substrates toward the c−-direction (N-polar) emitted at a longer peak wavelength than the on-axis m-plane substrates, indicating that the off-axis substrates have impact on enhancement of the indium incorporation in the InGaN/GaN QWs. The LED on the c−-5° off-axis substrate emitted at 457 nm under DC current of 20 mA and showed 0.7 nm red-shift from 1 to 20 mA. The c−-5° off LED showed an optical polarization ratio of 0.91, which is comparable to the nonpolar material.