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The indium tin oxide (ITO) transparent electrode layer on green and blue light-emitting diodes (LEDs) was patterned with various-sized periodic hole arrays, size ranging from 300 nm to 380 nm, using thermal nanoimprint lithography and inductively coupled plasma (ICP) etching processes. The imprinted resin was used as a mask layer and etch resistance of the imprinted resin was adjusted in order to control the tapered and enlarged etch profile of the ITO layer, since the tapered etch profile can improve the light extraction efficiency of the LED by prominent scatterings. Photoluminescence intensity from InGaN multi-quantum wells for the green LED structure showed that up to 4.6 times stronger emission was exhibited with the patterned ITO electrode, compared to the identical sample with an un-patterned blanket ITO electrode layer. An electroluminescence (EL) intensity of a blue LED sample witha patterned ITO electrode layer was increased up to 23% compared to that of the identical sample with an un-patterned blanket ITO electrode layer.

An epitaxial, laterally-overgrown (ELOG) GaN layer is deposited on a Si(111) substrate using high-dose, N þ ion implantation.ELOG GaN is deposited on a Si(111) wafer with implantation stripes by metal-organic (MO) CVD. The GaN layer on the N þ ion-implanted region is polycrystalline and acts as a mask for the ELOG process. This is attributed to the growth rate of the polycrystalline GaN being much slower than that of epitaxial GaN. After 120 min, complete coalescence is achieved with a flat surface. Scanning cathodoluminescence (CL) microscopy and high resolution X-ray diffraction (HRXRD) confirm the high optical and crystalline quality of the ELOG GaN layer.

The growth mode of europium (Eu)-doped GaN epitaxial films grown on a GaN template by rf plasma-assisted molecular beam epitaxy (PAMBE) was investigated with different III/V ratios under a constant Eu beam equivalent pressure ratio [P Eu/(P Eu+P Ga)]. The reflection high-energy electron diffraction (RHEED) patterns and atomic force microscopy (AFM) images revealed the transition of the growth mode from three-dimensional (3D) to step-flow/two-dimensional (2D) by increasing the III/V ratio. When the films were grown in the 3D growth mode, Eu concentrations estimated by Rutherford backscattering spectrometry/channeling (RBS/channeling) were almost constant, although the III/V ratios varied. However, when the growth mode was transferred from 3D to step-flow/2D, precipitates on the surface abruptly increased while the Eu concentration abruptly decreased, indicating the abrupt degradation of Eu-incorporation in the film. Luminescence sites of Eu3+ were sensitive to the III/V ratio, and Eu atoms have different luminescence sites in both growth modes. Furthermore, luminescence efficiency abruptly increased when the growth mode was transferred from 3D to step-flow/2D.

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