GaN-based light-emitting diodes (LEDs) grown on Si(111) substrates were fabricated with a vertical electrode method by using wafer bonding technology. The fabricated vertical LEDs showed a lower operating voltage and larger light output power than conventional LEDs due to enhancement in current spreading and reduction in tensile strain. The light output power of the vertical structured LEDs was 2.6 times higher than that of conventional LEDs, with an operating voltage at 20 mA reduced from 3.5 to 3.2 V.

We investigated the effects of the well protection layer (WPL) and electron reservoir layer (ERL) on the emission properties of InGaN/GaN green multiple quantum wells (MQWs). In order to increase their emission wavelength by preventing the volatile InGaN well, a thin GaN WPL was coated subsequently on each well layer at the same temperature before ramping-up the temperature to grow the GaN barrier. It was found that the WPL directly influenced the indium content and optical properties of the MQW. The indium content was in fact increased, as was evident from the x-ray diffraction and photoluminescence experiments. Then, to explore the possibility of enhancing the quantum efficiency by increasing the electron capture rate, a superlattice ERL composed of ten pairs of InGaN/GaN was embedded between the MQW and n-GaN. The electroluminescence intensity of the green light emitting diode with the ERL was up to three times higher than that of the diode without the ERL. These results imply that the carrier capture by the MQW is significantly improved by the additional superlattice ERL, which consequently leads to the enhancement of the quantum efficiency.

We demonstrate that Pd nanoparticle/single-walled carbon nanotubes (Pd-SWCNTs) can be used to improve the quality of α-Ga2O3 crystals using halide vapor phase epitaxy (HVPE) methods. We employed Pd-SWCNTs as the nanoepitaxial lateral overgrowth (ELOG) mask instead of typical dielectric microsize materials, such as SiNx or SiO2. Nano-ELOG Pd-SWCNTs were deposited on a (0001) buffer layer using nanospray coating. Cs-corrected TEM (transmission electron microscopy) analysis revealed that the crystal quality of regrown α-Ga2O3 improved owing to both the blocking of dislocations by the nano-ELOG in the Pd NPs and the dislocation bending by the inclined facets. This simple yet effective technique is believed to be applicable to various growth systems and will find diverse applications in other crystal growth processes.

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