Surface roughness of gallium nitride with volcano-like protrusions formed by KrF excimer laser etching

Use of deep ultraviolet (248 nm) KrF laser irradiation to roughen vertical GaN-based LEDs surface with volcanolike protrusions for light output (Lop) improvement was proposed and demonstrated. After pulse irradiations of KrF laser (750-850 mJ/cm2), the rate of electron-hole pair recombination at sites with dislocation defects is greater than for crystalline GaN, favoring for the formation of GaOx, and in turn, resulting in a relatively lower etching rate therein and leading to a roughened surface with volcano-like protrusions. Typical diameter/height and density of protrusions are around 2~4 μm/2 μm and 106 cm-2. Through the use of KrF laser and KOH etching, an enhancement in the root-meansquare surface roughness by 250 times and an improvement in Lop by 25% at 750 mA were obtained. It is expected that the surface roughness of Gallium Nitride by KrF excimer laser technology would be a potential candidate for the fabrication of high power GaN-based LEDs for solid-state lighting in the near future.

[1]  Hao-Chung Kuo,et al.  Enhanced light output power of GaN-based vertical-injection light-emitting diodes with a 12-fold photonic quasi-crystal by nano-imprint lithography , 2009 .

[2]  D. H. Mash,et al.  Light-emitting diodes , 1977, Nature.

[3]  Yong-Hee Lee,et al.  Laser Liftoff GaN Thin-Film Photonic Crystal GaN-Based Light-Emitting Diodes , 2008, IEEE Photonics Technology Letters.

[4]  Geun Young Yeom,et al.  Effect of the surface texturing shapes fabricated using dry etching on the extraction efficiency of vertical light-emitting diodes , 2008 .

[5]  Shuji Nakamura,et al.  Cone‐shaped surface GaN‐based light‐emitting diodes , 2005 .

[6]  Shui-Jinn Wang,et al.  Use of patterned laser liftoff process and electroplating nickel layer for the fabrication of vertical-structured GaN-based light-emitting diodes , 2005 .

[7]  Jing Li,et al.  III-nitride blue microdisplays , 2001 .

[8]  Shuji Nakamura,et al.  Room-temperature continuous-wave operation of InGaN multi-quantum-well structure laser diodes with a lifetime of 27 hours , 1997 .

[9]  William S. Wong,et al.  Structural and chemical characterization of free-standing GaN films separated from sapphire substrates by laser lift-off , 2000 .

[10]  Takashi Mukai,et al.  Blue InGaN-based laser diodes with an emission wavelength of 450 nm , 2000 .

[11]  Chia-Feng Lin,et al.  Effective heat dissipation and higher light extraction efficiency of GaN vertical light emitting diodes for solid state lighting applications , 2009 .

[12]  J S Kwak,et al.  Light-extraction enhancement of vertical-injection GaN-based light-emitting diodes fabricated with highly integrated surface textures. , 2008, Optics letters.

[13]  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 .

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

[15]  N. Cheung,et al.  Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off , 1999 .