Enhancement of InN Luminescence by Introduction of Graphene Interlayer.

Indium nitride (InN) luminescence is substantially enhanced by the introduction of a multilayer graphene interlayer, mitigating the lattice mismatch between the InN epilayer and the Gallium nitride (GaN) template on a sapphire substrate via weak van der Waals interaction between graphene and nitride layers. The InN epilayers are deposited by radio-frequency plasma-assisted molecular beam epitaxy (MBE), and are characterized by spatially-resolved photoluminescence spectroscopy using confocal microscopy. A small blue shift of the emission band from the band gap evidences a low density of equilibrium carriers, and a high quality of InN on multilayer graphene. A deposition temperature of ~375 °C is determined as optimal. The granularity, which is observed for the InN epilayers deposited on multilayer graphene, is shown to be eliminated, and the emission intensity is further enhanced by the introduction of an aluminum nitride (AlN) buffer layer between graphene and InN.

Less strained and more efficient GaN light-emitting diodes with embedded silica hollow nanospheres.

Light-emitting diodes (LEDs) become an attractive alternative to conventional light sources due to high efficiency and long lifetime. However, different material properties between GaN and sapphire cause several problems such as high defect density in GaN, serious wafer bowing, particularly in large-area wafers, and poor light extraction of GaN-based LEDs. Here, we suggest a new growth strategy for high efficiency LEDs by incorporating silica hollow nanospheres (S-HNS). In this strategy, S-HNSs were introduced as a monolayer on a sapphire substrate and the subsequent growth of GaN by metalorganic chemical vapor deposition results in improved crystal quality due to nano-scale lateral epitaxial overgrowth. Moreover, well-defined voids embedded at the GaN/sapphire interface help scatter lights effectively for improved light extraction, and reduce wafer bowing due to partial alleviation of compressive stress in GaN. The incorporation of S-HNS into LEDs is thus quite advantageous in achieving high efficiency LEDs for solid-state lighting.

Catalyst-free metal-organic chemical vapor deposition growth of InN nanorods.

We demonstrated the successful growth of catalyst-free InN nanorods on (0001) Al2O3 substrates using metal-organic chemical vapor deposition. Morphological evolution was significantly affected by growth temperature. At 710 degrees C, complete InN nanorods with typical diameters of 150 nm and length of approximately 3.5 microm were grown with hexagonal facets. theta-2theta X-ray diffraction measurement shows that (0002) InN nanorods grown on (0001) Al2O3 substrates were vertically aligned along c-axis. In addition, high resolution transmission electron microscopy indicates the spacing of the (0001) lattice planes is 0.28 nm, which is very close to that of bulk InN. The electron diffraction patterns also revealed that the InN nanorods are single crystalline with a growth direction along (0001) with (10-10) facets.