Fabrication and optical study of ingan-based low dimensional quantum structures grown on GaN pyramids

Abstract

The group III-nitrides such as AlN, GaN, and, InN as wide bandgap materials have recently attracted considerable attention as promising materials for optoelectronic devices due to their good thermal, chemical, and, mechanical stabilities, as well as their wide range of bandgap energy from ultra-violet, to visible, and to infrared. However there have been drawbacks in the III-nitrides such as large number of dislocations due to lattice mismatches with various substrates, poor internal quantum efficiency of InGaN with high In-content, and poor recombination rate due to electric polarization. There have been numerous approaches to overcome the drawbacks in the nitrides. We proposed the nano- and micro-pyramid structures as a solution for many drawbacks in the nitrides. InGaN-based low dimensional structures and semi-polar facets were fabricated and characterized by growing InGaN on GaN pyramid structures. In this study, the InGaN-based semi-polar facets were systematically studied and applied to broadband emission by using the hexagonal annular structure grown on the ring pattern, and the InGaN-based low dimensional structures were studied and applied to electrically-driven device by using the nano-pyramid structure grown on the hole pattern. Hexagonal pyramid structures of GaN were fabricated through the selective-area growth method of metal-organic chemical vapor deposition. Various kinds of pyramid structures such as the nano- pyramid structure of 260 nm, micro- pyramid structure of 2.8 μm, and the hexagonal annular structures were obtained depending on size dimension and shape of the patterning. Optical characterization was performed through the photoluminescence (PL), time-resolved PL, and cathodoluminescence. To study the growth mechanism and general properties of the pyramid structure, we carried out comparative study of InGaN on nano-pyarmid and planar structure with the same growth condition. The In-content of pyramid structure was 31.25 % which was much...