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R9.39.1

Position Controlled GaN Nano-Structures Fabricated by Low Energy Focused Ion Beam System. Takahiro Nagata1, Parhat Ahmet2, Takashi Koida4, Shigefusa F. Chichibu3,4, and Toyohiro Chikyow1,2 1 CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 560-0082, Japan. 2 National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047, Japan. 3 Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan. 4 NICP, ERATO, Japan Science and Technology Corporation (JST), Fujimi, Chiyoda 102-0071, Japan. ABSTRACT We have demonstrated position controlled GaN nano structures with a combination of surface treatments and nucleation sites control assisted by low energy focused ion beam. Ga ions in the range of 100 eV - 10 keV were irradiated onto the surface of the As-terminated Si (100) to create the nucleation sites. The deposited Ga atoms migrated on the surface and were trapped at the nucleation sites to form Ga droplets. Subsequently an excited atomic nitrogen source was supplied to the surface. By SEM observation, the GaN microcrystals of diameter about 800 nm were found to be allocated every 2 µm periodically on the substrates, and cathodoluminescence peaks from GaN nano structures were observed. INTRODUCTION GaN and related compounds have been identified as promising materials for future optical devices [1], and nano structured GaN has also a great potential to realize an innovative optical devices. However, ordered nano structures of GaN or position controlled GaN nano structures must demonstrate their practical applications. The critical issues are nucleation site control and selective growth from the sites. As a suitable fabrication method, a low energy focused ion beam (LE-FIB) with a combination of the droplet epitaxy was proposed [2]. The LE-FIB systems have the ability to mill a few mono layers of a surface selectively by ion sputtering (nucleation site control) and can deposit materials via a ion-induced deposition (selective growth) [3,4]. GaAs nano crystals grown from Ga droplets on a Se- or S-terminated GaAs and an As terminated Si surface by the LE-FIB systems have been reported [2,5,6].

R9.39.2

In this paper, we report the fabrication and optical properties of position controlled Ga droplets and GaN nano structures on the As-terminated Si surface or silicon nitride deposited Si surfaces by using the combination of the droplet epitaxy and the LE-FIB systems. EXPERIMENTAL DETAILS A Si (001) wafer was used as the substrate. After a conventional cleaning process, a rectangle shaped Si (001) sample was dipped in a HF solution (HF:H2O=1:9) and loaded into MBE system. The sample was heated up to 1200°C and flashed for 3 s by direct current in an As molecule atmosphere. Subsequently the temperature of the sample was reduced to 400°C to achieve an As termination of the Si surface. The sample was transferred to the LE-FIB chamber and the sample surface was irradiated by Ga ions with 100 eV at room temperature