Growth of N-polarity InN by ArF-laser assisted MOVPE
|Akio Yamamoto 1,2, Ken Kasashima 1, Masayoshi Miyanishi 1, Akihiro Hashimoto 1|
1. University of Fukui (U. Fukui), 3-9-1 Bunkyo, Fukui 910-8507, Japan
To overcome the problem of the low decomposition rate of NH3, we have developed the laser-assisted MOVPE (la-MOVPE) where an ArF excimer laser (λ=193 nm) dissociates NH3 photolytically . A film can be grown in a wide range of growth temperature, from RT to 700ºC. This growth technique provides a growth rate of more than 0.5 μm/h just by flowing a very little amount (100 sccm) of NH3. Thus, the la-MOVPE is promising as a new growth technique for InN. In this paper, we report that, by employing ArF-laser assisted nitridation of sapphire substrate, an N-polarity InN film can be grown by the ArF-laser assisted MOVPE. Using a la-MOVPE system, an InN film is grown at 600ºC on (0001) sapphire substrates. An ArF excimer laser with an energy 50 mJ/pulse and a repetition rate 20 Hz is introduced parallel to the substrate surface. The surface morphology of a grown InN film is found to be markedly dependent on the nitridation conditions for sapphire substrate. When no nitridation is made, the surface of a grown InN film is very rough and many In droplets are seen on it. A film with a mixture of rough-surface regions with In droplets and smooth-surface regions is grown on the substrate nitrided thermally at 1000ºC for 30 min. By employing the ArF-laser irradiation to the NH3 flow during the substrate nitridation at 1000ºC for 30 min, a smooth surface region is expanded to the entire surface of a film. The smooth surface is found to be stable at a growth temperature higher than 700ºC. The KOH etching of grown films reveals that the smooth surface has a 5-10 time higher etching rate than the rough one. These facts indicate that a film with the smooth surface has N-polarity. Thus, the ArF-laser assisted nitridation of sapphire substrate results in the successful growth of N-polarity InN by MOVPE.  A. G. Bhuiyan et al., Jpn. J. Appl. Phys. 42, 7284 (2003).
Presentation: poster at E-MRS Fall Meeting 2005, Symposium A, by Akio Yamamoto
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-20 02:53 Revised: 2009-06-07 00:44