III-nitride blue and UV photonic-crystal light-emitting diodes

Abstract

We report on the successful nano-fabrication and characterization of III-nitride blue and ultraviolet (UV) photonic crystal light emitting diodes (PC-LEDs) using electron beam lithography and inductively coupled plasma dry etching. Triangular arrays of holes with different diameters/periodicities were etched on the LEDs. Optical measurements on the photonic crystals (PCs) performed using near-field scanning optical microscopy (NSOM) showed a 60° periodic variation with the angle between the propagation direction of emission light and the PCs lattice. Under optical pumping, an unprecedented enhancement factor of 20 in emission light intensity of wavelength 475 nm was achieved at room temperature with emission light parallel to the Γ-K direction of the PCs lattice. Guided by the optical pumping results, new design geometry of LEDs with PCs has been employed to optimize the light extraction. Enhancement in optical power of current injected blue and UV PC-LEDs over conventional LEDs is discussed. It was observed that the optical enhancement factor depends strongly on the PC lattice constant and hole size. The achievement of nitride photonic crystal emitters with enhanced light extraction efficiency is expected to benefit many new applications of III-nitrides including solid-state lighting for general illumination and photonic integrated circuits operating in the visible and UV spectral regions.