Nonpolar and semipolar LEDs

A polarization-induced electric field fundamentally limits nitride-based LEDs grown on the c-plane. Nonpolar and semipolar LEDs have potential for superior performance through high internal quantum efficiency over a wide spectral region and low efficiency droop due to improved carrier transport and high compositional homogeneity. Nonpolar and semipolar LEDs possess unique electroluminescent characteristics such as polarized light emission and reduced wavelength shift due to the lift of degeneracy in the conduction band and mitigated quantum-confined Stark effect. In epitaxial growth, the surface morphology and defect generation mechanism on nonpolar and semipolar planes differ from those on the c-plane due to the anisotropic surface geometry and tilted slip systems. LED chips are designed to enhance the light extraction efficiency of nonpolar and semipolar LEDs grown on free-standing GaN substrates.