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Room temperature stimulated emission from self-organized GaN nano-columns grown on (111) Si substrate

Makoto Tada 1Akihiko Kikuchi Katsumi Kishino 

1. Sophia University, 7-1, Koi-cho, Chiyoda-ku, Tokyo 102-8554, Japan


High optical quality self-organized GaN nano-columns were successively grown on (111) Si substrates by an rf-plasma assisted molecular beam epitaxy. The intensity of room temperature photoluminescence (PL) of the nano-columns was 500 times stronger than that of typical GaN film grown by MOCVD. Furthermore, room temperature stimulated emission was observed with a very low threshold excitation power density of 350kW/cm2. This superior optical property of GaN nano-columns on Si is comparable to that of the optimized GaN nano-columns on (0001) sapphire reported recently [1].
GaN nano-columns with a diameter, density and height of ~100nm, 5~12x109/cm2, and ~1.6μm, respectively, were grown on (111) Si substrate without native oxide (sample A), and with native oxide (sample B). After a Ga deposition, active nitrogen was irradiated for 60s to form GaN dots as nucleation layer at 530oC, then GaN nano-columns were grown at high temperature for 60min. The c-axis of nano-columns was perpendicular to the substrate surface for sample A and randomly tilted to the perpendicular of the substrate surface for B.
Strong PL emission was observed at 363~364nm from both samples for low excitation condition (1.3W/cm2). The peak intensity was 500 times stronger than that of a 3.7μm-thick GaN films grown by MOCVD on a (0001) sapphire with a dislocation density of 3~5x109/cm2. For higher excitation condition, stimulated emission was observed at 369nm with a threshold of 350kW/cm2 for sample A. While no stimulated emission was observed up to 6MW/cm2 for sample B. For reference, the threshold of stimulated emission of the MOCVD-GaN film and optimized GaN nano-columns on (0001) sapphire were 1.6MW/cm2 and 200kW/cm2, respectively.
These results suggesting that high performance light emitting devices on low-cost conductive substrate can be realized by GaN-based nano-columns on Si substrates.
[1] A. Kikuchi and K. Kishino, Int. Symp. on Blue Laser and LED, B3-1, March 2004.


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Presentation: oral at E-MRS Fall Meeting 2004, Symposium C, by Akihiko Kikuchi
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 12:53
Revised:   2009-06-08 12:55