Nano Imprint Lithography (NIL) is a promising technology that combines low costs with high throughput for
fabrication of sub 100 nm scale features. One of the first application areas in which NIL is used is manufacturing
of various types of LED's. The wafers used for producing LED's are typically III/V semiconductor materials
grown with epitaxial processes. These types of substrates suffer from growth defects like hexagonal spikes, vpits,
waferbowing, atomic steps and surface corrugations on a scale of few 10 μm or even large islands of
irregularities. The mentioned irregularities are particularly disturbing when NIL based processes are utilized to
create patterns onto the wafer surface. The nanopatterns created by NIL can be applied to control metal organic
vapour phase epitaxy (MOVPE) growth of GaN nanorods. This paper will show that NIL is an excellent
technology to produce nanopatterned GaN substrates highly suitable to grow defect free arrays of positioncontrolled
nanorods for ultrahigh brightness LED applications.
Two optical devices with nano-scale subwavelength structures have been fabricated by using nanoimprint lithography (NIL). (1) Wire grid polarizer (WGP) is one of key optical components for projection displays with liquid crystal micro-display. Although WGP with 140 nm pitch is commercially available now, it still poses a problem with low extinction ratio (ER) for blue color. Since the ER can be increased by reducing the pitch, fabrication of a WGP with 100 nm pitch was attempted by NIL. We successfully developed thermal nanoimprint and aluminum dry etching processes. Fabricated WGPs showed twice higher ER than 140 nm pitch one. (2) Photonic crystal (PC) structures on LED have been known to enhance the light extraction significantly. Although e-beam lithography has been used for the proof of principle, it is far from real production method. We applied thermal NIL to fabricate PC structures in p-GaN layer of green LED. To identify the PC effect, two structures were fabricated and compared. One structure makes the green light of 525 nm wavelength fall within the photonic band gap (PBG) while the other puts it outside of PBG. The former structure showed 9-fold increment of photoluminescence compared to LED without PC structures, while the latter showed only 6-fold increment
Conference Committee Involvement (2)
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics III
25 January 2010 | San Francisco, California, United States
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II
26 January 2009 | San Jose, California, United States
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