MOVPE에 의한 GaN 피라미드 구조 위 GaN rod의 선택적 결정성장에 관한 연구

Abstract

One dimensional GaN nanostructures have recently attracted much attention because of their potential applications optoelectronic devices in the nanoscale. GaN nanowires have been synthesized by many kinds of synthetic methods. However, most of the nanostructures tend to be randomly distributed and the density of nanostructures was not easy to control in those fabrication methods. It is very important to control the position and the density of nanostructures. In our newly developed method, the GaN rods could be grown only on apex of GaN pyramids by using of metal catalysts. The hexagonal GaN pyramids were selectively grown on a GaN template with SiO2 dot patterns (diameter: 3micrometer) by metal organic vapor phase epitaxy(MOVPE). After the formation of GaN pyramids, SiO2 film was deposited on the GaN pyramids and followed by photo-resist (PR) coating. PR could be partially removed only on the top area without using of any mask. Au was evaporated after removing the SiO2 on the apex of the GaN pyramids. After the conventional lift-off process, GaN rods were grown by using of metal catalyst remained only on the apex of the GaN pyramids. The growth temperature was 800 °C. For the growth of GaN rods trimethylgallium (TMGa) and ammonia (NH3) were used as precursors and nitrogen was used as a carrier gas. It was observed that there were preferred GaN rods orientations toward <1-100> directions. The GaN rods had triangular cross section enclosed with (11-22), (-1-122) and (0001) side facets. A particular feature was that each rod has sharp edge at its very end. We found that the GaN rods could be formed not by vapor-liquid-solid (VLS) process but Ga-Au intermediate state. This work opens up new growth methods for position and density controlled III-nitride nano- and micro-structures which have potential use in high functional devices, such as field emitters and gas sensors.