Application of Nanosphere Lithography to LED Surface Texturing and to the Fabrication of Nanorod LED Arrays

In this study, the process of nanosphere lithography was developed and applied to LED surface texturing and nanorod device fabrication. We observed a texture-size-dependent improvement of total light output. While the increase of output optical power from the textured LEDs can be attributed to surface roughening in the GaN-air surface and to the increase of internal quantum efficiency as the strain is relaxed with the surface texturing, the size-dependent device performance is related to the interaction of generated photons with the textured surface. We further etched through the p-GaN and quantum well region to form p-i-n nanorods on the sample. By inserting a spacer to prevent p-type contact from shorting the n-GaN, we successfully demonstrated nanorod LED arrays. For such a device, a narrower radiation profile was demonstrated from the nanorod LED array as compared with that from the planar LED. The result is associated with the vertical guiding effect along the nanorod cylinder and the Bragg scattering of photons extracted from the sidewall by the rest of the rods. Furthermore, the electroluminescence spectra showed a nearly constant peak wavelength of the nanorod LED arrays, which is due to the suppression of the effect of quantum confined Stark effect.

[1]  Yan-Kuin Su,et al.  Improved light output power of InGaN/GaN MQW LEDs by lower temperature p-GaN rough surface , 2004 .

[2]  Marc Lamy de la Chapelle,et al.  Silica-assisted catalytic growth of oxide and nitride nanowires , 2001 .

[3]  Seong-Ju Park,et al.  Selective wet etching of p-GaN for efficient GaN-based light-emitting diodes , 2006, IEEE Photonics Technology Letters.

[4]  Hongxing Jiang,et al.  Enhanced light extraction in III-nitride ultraviolet photonic crystal light-emitting diodes , 2004 .

[5]  Vapor-Liquid-Solid Mechanisms: Challenges for Nanosized Quantum Cluster/Dot/Wire Materials , 2007 .

[6]  Chia-Chun Chen,et al.  Large‐Scale Catalytic Synthesis of Crystalline Gallium Nitride Nanowires , 2000 .

[7]  Ru-Chin Tu,et al.  Enhanced output power of InGaN-GaN light-emitting diodes with high-transparency nickel-oxide-indium-tin-oxide Ohmic contacts , 2003 .

[8]  Growth of gallium nitride nanorods by metalorganic molecular beam epitaxy , 2006 .

[9]  D. Lin,et al.  High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure , 2006 .

[10]  H. Kuo,et al.  Fabrication of InGaN/GaN nanorod light-emitting diodes with self-assembled Ni metal islands , 2007 .

[11]  Chii-Chang Chen,et al.  Light enhancement by the formation of an Al oxide honeycomb nanostructure on the n-GaN surface of thin-GaN light-emitting diodes , 2007 .

[12]  Jian-jang Huang,et al.  GaN nanorod light emitting diode arrays with a nearly constant electroluminescent peak wavelength. , 2008, Optics express.

[13]  Jian-jang Huang,et al.  Improvement of External Extraction Efficiency in GaN-Based LEDs by $ \hbox{SiO}_{2}$ Nanosphere Lithography , 2008, IEEE Electron Device Letters.

[14]  Dong-Sing Wuu,et al.  Efficiency Improvement of GaN-Based LEDs with ITO Texturing Window Layers Using Natural Lithography , 2006, IEEE Journal of Selected Topics in Quantum Electronics.

[15]  T. Baba,et al.  Efficiency enhancement in a light-emitting diode with a two-dimensional surface grating photonic crystal , 2004 .

[16]  Wonseok Lee,et al.  Influence of growth temperature and growth rate of p-GaN layers on the characteristics of green light emitting diodes , 2006 .

[17]  Chih-Chung Yang,et al.  Strain relaxation and quantum confinement in InGaN/GaN nanoposts , 2006 .

[18]  Seong-Ju Park,et al.  Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface , 2003 .

[19]  H. Kuo,et al.  Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask , 2007 .

[20]  Isamu Akasaki,et al.  Quantized states in Ga 1 − x In x N / GaN heterostructures and the model of polarized homogeneous quantum wells , 2000 .

[21]  Synthesis of aligned GaN nanorods on Si (111) by molecular beam epitaxy , 2005 .

[22]  JianJang Huang,et al.  InGaN–GaN Nanorod Light Emitting Arrays Fabricated by Silica Nanomasks , 2008, IEEE Journal of Quantum Electronics.