Optical-Emission Properties of GaN-Based Nanopillar Light-Emitting Diodes Prepared on Non-Polished and Non-Single-Crystalline Substrates

GaN-based nanopillar crystals are directly grown on multicrystalline Si and amorphous-carbon-coated graphite substrates whose surfaces are not mirror-polished. Light-emitting diodes (LEDs) of a double-hetero structure are prepared from the nanopillar crystals, and their optical–emission properties are investigated. Despite the substrate type and surface conditions, moderate light emissions are obtained from nanopillar LEDs though the light emissions are not always homogeneous, especially in the LEDs prepared on the graphite-based substrate. Nevertheless, these results will lead to realizations of novel large-area light-emitting devices.