Epitaxial GaN Microdisk Lasers Grown on Graphene Microdots

Hyeonjun Baek, Chul-Ho Lee, Kunook Chung, and Gyu-Chul Yi "Epitaxial GaN Microdisk Lasers Grown on Graphene Microdots", Nano Letters, 13(6), 2782-2785 (2013.05.14)

본 연구에서는 graphene microdot을 nucleation layer로 이용하여 비정질의 SiO2 층 위에 고품질의 GaN microdisk를 성장하였다. Epitaxial lateral overgrowth 과정을 통해 graphene microdot 위에서 성장된 GaN의 광학적, 구조적 성질을 향상 시킬 수 있음을 cathodoluminescence와 transmission electron microscopy을 이용하여 확인 하였다. 또한, 형성된 고품질의 GaN microdisk을 이용하여 laser를 제조할 수 있음을 증명하였다. 본 연구는 비정질의 기판 위에서도 고품질의 GaN를 성장 하여, 기판에 구애 받지 않고 원하는 기판 위에 고품질의 화합물 반도체를 성장하는 방법을 제시한다 할 수 있다.

Abstract
Direct epitaxial growth of inorganic compound semiconductors on lattice-matched single-crystal substrates has provided an important way to fabricate light sources for various applications including lighting, displays and optical communications. Nevertheless, unconventional substrates such as silicon, amorphous glass, plastics, and metals must be used for emerging optoelectronic applications, such as high-speed photonic circuitry and flexible displays. However, high-quality film growth requires good matching of lattice constants and thermal expansion coefficients between the film and the supporting substrate. This restricts monolithic fabrication of optoelectronic devices on unconventional substrates. Here, we describe methods to grow high-quality gallium nitride (GaN) microdisks on amorphous silicon oxide layers formed on silicon using micropatterned graphene films as a nucleation layer. Highly crystalline GaN microdisks having hexagonal facets were grown on graphene dots with intermediate ZnO nanowalls via epitaxial lateral overgrowth. Furthermore, whispering-gallery-mode lasing from the GaN microdisk with a Q-factor of 1200 was observed at room temperature.