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InGaN/GaN nanocolumn LEDs and selective area growth of GaN nano-crystals by rf-plasma assisted molecular beam epitaxy
|Akihiko Kikuchi 1,2,3, Hiroto Sekiguchi 1, Katsumi Kishino 1,2,3|
1. Sophia University, Department of Engineering and Applied Sciences, 7-1, Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
III-nitride nano-crystals, such as nanocolumns  are attractive candidate for opto-electronic devices, for the sake of their dislocation free-nature, strain-relaxation effect and high light extraction efficiency. For the application of nano-crystals, suitable device structure and accurate shape and position control are required.
Recently we have fabricated InGaN/GaN nanocolumn LEDs on flexible metal sheet. After the growth of n-GaN nanocolumn and InGaN/GaN quantum disks on (111) Si substrate by rf-plasma assisted molecular beam epitaxy, the lateral growth of p-GaN was enhanced to make continuous film at the top surface . Pt/Au (50mm) electrode was formed on the p-side surface and then Si was selectively removed. After filling the interstice of n-GaN nanocolumns with spin on glass, tips of the nanocolumns were exposed in circular (f=400mm) then ITO transparent electrodes were deposited. The nanocolumn LED showed red (663nm) emission under 10mA DC drive.
The size and position fluctuation of self-assembled InGaN/GaN nanocolumns cause broadening of emission spectra. Selective area growth (SAG) of GaN nano-crystals is a key technology to overcome this problem. For the SAG of nano-crystals, (0001) GaN templates coated with nano-patterned Ti (~5nm) were used as substrate. Holes or stripe windows with diameter or width of around 100~400nm were open to appear the GaN surface. When the growth temperature was above 900oC, GaN nano-crystals were grown only on the window area with side facets normal to the substrate surface. Well aligned nanocolumns  and plate-like thin nano-crystals (nanowalls)  were grown.
 M. Yoshizawa et al, Jpn. J. Appl. Phys. 36 (1997) L459.  A. Kikuchi et al, Jpn. J. Appl. Phys. 43 (2004) L1524.  H. Sekiguchi et al, Appl. Phys. Express 1, (2008) 124002.  A. Kikuchi et al, MRS Fall Meeting, Q4.6, USA (2007).
Presentation: Invited oral at E-MRS Fall Meeting 2009, Symposium A, by Akihiko Kikuchi
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-22 16:59 Revised: 2009-06-07 00:48