Nonperiodic binary optical structures for enhancing light extraction of emitters

This paper presents a new method of designing binary optical structures to improve light extraction efficiency for emitters. Using this method a novel binary optical structure is generated. Such structures with an approximate width of 300 nm, are non-period and small enough in size so that they do not generate diffraction orders other than the zero order. They are also insensitive to polarization. They serve as an antireflection layer, sending light outward that would otherwise be absorbed within the device. The experimental devices were GaN based LEDs emitting at 460nm. The non-periodic binary structures and some periodic structures such as triangle-lattice Photonic Crystals (PC), 12-fold Quasi-periodic Photonic Crystals (QPC) are fabricated on the same sapphire side of a LED's flip chip with a Focus Ion Beam (FIB) for comparison. The surface profile of the structures was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Near field scanning optical microscopy (NSOM) was used to measure the output spectral properties of the devices. Electrical Luminescence (EL) measurements show that the greatest enhancement of emission light intensity was achieved in non-periodic binary structures. This increase was 60~135% at room temperature. It demonstrates that this Non-Periodic Binary Optical Structures will be useful for fabricating high efficient GaN-based LED.

[1]  H. Miyake,et al.  Antireflection structure of self-organized GaN nanotips , 2002, 2002 Conference on Optoelectronic and Microelectronic Materials and Devices. COMMAD 2002. Proceedings (Cat. No.02EX601).

[2]  S. Denbaars,et al.  Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening , 2004 .

[3]  K. Hane,et al.  Subwavelength Antireflection Gratings for Light Emitting Diodes and Photodiodes Fabricated by Fast Atom Beam Etching , 2001, Digest of Papers. Microprocesses and Nanotechnology 2001. 2001 International Microprocesses and Nanotechnology Conference (IEEE Cat. No.01EX468).

[4]  Yong-Hee Lee,et al.  Two-dimensional photonic crystal semiconductor lasers: computational design, fabrication, and characterization , 2002 .

[5]  K. Hane,et al.  Subwavelength antireflection gratings for photovoltaic cells in visible and near-infrared wavelengths , 2002, 2002 International Microprocesses and Nanotechnology Conference, 2002. Digest of Papers..

[6]  Yong-Hee Lee,et al.  Enhancement of light extraction from two-dimensional photonic crystal slab structures , 2002 .

[7]  Andrew J. Waddie,et al.  Design and fabrication of diffractive optical elements , 1997 .

[8]  Kengo Nozaki,et al.  Ultralow threshold and single-mode lasing in microgear lasers and its fusion with quasi-periodic photonic crystals , 2003 .

[9]  Olof Bryngdahl,et al.  Electromagnetic diffraction analysis of two-dimensional gratings , 1993 .

[10]  K. Hane,et al.  Sub-wavelength structure for anti-reflection fabricated by fast atom beam etching , 2001, Technical Digest. CLEO/Pacific Rim 2001. 4th Pacific Rim Conference on Lasers and Electro-Optics (Cat. No.01TH8557).

[11]  K. Hane,et al.  High efficient light-emitting diodes with antireflection subwavelength gratings , 2002, IEEE Photonics Technology Letters.

[12]  Z. J. Yang,et al.  Effects of symmetry of GaN-based two-dimensional photonic crystal with quasicrystal lattices on enhancement of surface light extraction , 2006 .

[13]  Kazuhiro Hane,et al.  100 nm period silicon antireflection structures fabricated using a porous alumina membrane mask , 2001 .

[14]  Kazuhiro Hane,et al.  Broadband antireflection for III-V semiconductors by subwavelength surface grating structures , 2003, 3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of.

[15]  Eli Yablonovitch,et al.  Analysis of photonic crystals for light-emitting diodes using the finite-difference time domain technique , 1998, Photonics West.

[16]  Jinsong Liu.  Design and fabrication of diffractive optical elements , 2004 .

[17]  Axel Scherer,et al.  Surface plasmon enhanced LED , 2000, CLEO 2000.