Si(111) 기판 위 자가유도에 의한 GaN 나노막대 성장시 AlN 핵층 효과

Abstract

Si(111) 기판을 사용 GaN 나노막대를 MBE법으로 성장하였으며,나노막대의 AlN핵 유무에 대하여 구조적 광학적 특성은 reflection high-energy electron diffraction, scanning electronics microscopy,photoluminescence (PL)로 조사하였다. AlN 핵이 있는 경우 GaN 나노막대성장시 초기 2차원 성장은 핵이 없는 경우와 비교해 더 길었으며,나노막대의 폭과 길이는 커졌으나 밀도는 오히려 낮아졌다. PL 측정에서도 AlN 핵이 있는 경우 I2 형 적층결함과 결함관련 노란밴드발광을 관측하였다. 이는 AlN 핵이 있는 경우 GaN 나노막대 초기 성장시Si 에 비해 격자 부정합 차가 적기 때문에 큰 핵생성과 더불어 계속성장시 수직성장되면서 나노막대간 결합이 쉽게 일어난 것으로 설명된다. 격자상수 변화 및 구조적 특성과 같은 결과들은 나노막대의 성장구조를이해하는데 중요한 정보를 제공할 것이다.

We investigated the structural and the optical properties of GaN nanorods with and without AlN a nucleation layer grown on Si(111)substrates by using molecular beam epitaxy. The structural and the optical properties were measured by using reflection high-energy electron diffraction, scanning electronics microscopy and photoluminescence (PL). From the results, we found that the growth time of the 2-D growth mode of GaN with an AlN layer was longer than that without AlN layer. GaN nanorods with an AlN layer were wider and longer, but the number density of GaN nanorods sas lower than that without AlN layer. Also, by using PL measurements, we found an emission peak related to defects, such as stacking faults, and a yellow band in GaN nanorods with an AlN nucleation layer. This result is due to the small difference in lattice constants between GaN nanorods with an AlN layer and GaN grown on a Si substrate. For a further increase in thickness, we could observe a transition of the islands into vertical growth of the GaN layer and an evolution of longer nanorods with defects of stacking faults through coarsening processes. The variation and the strain and the structural properties will provide fruitful information to understand the growth mechanism of various materials' nanorods.