A three-dimensional model with finite difference and time domain was established to investigate the enhancement of the light output intensity of GaN light-emitting diodes ͑LEDs͒ with bottom pillar ͑BP͒ structure. Through comparing the normalized light extraction intensity of GaN LEDs with or without BP in different dimensions, the theoretical results show that the light output intensity in the LED with BP structure involved could be enhanced by about 30%. The influence of BP structure on the light output intensity of a LED could be explained by the physical model of light interaction. In addition, the experimental results also show the same trend to the theoretical calculations.

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In this paper, a simple design cylindrical dielectric resonator antenna (CDRA) with wide aperture‐coupled for broadband applications has been proposed. For improving impedance matching, microstrip feed‐line was designed as a fork‐like to obtain two resonant modes excitation and lead to a wider impedance bandwidth. Experimental results indicate that the measured bandwidth is 10.6% (S11 < −10 dB) with broadside radiation pattern. Additionally, the proposed antenna gain is near 7.9 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1064–1067, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22359

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The activation of Mg-doped GaN using a thin Ni film has been investigated. The results show that the Ni film significantly enhances the hydrogen desorption from the GaN film, which could improve the hole concentration and the resistivity of a p-GaN film. By means of a selective high resistivity region (SHRR) with no Ni catalyst involved, the current blocking layer is thus simply developed beneath the p-pad electrode of the GaN-based light-emitting diodes (LEDs). The light-output intensity for the LED chip with a SHRR is significantly increased as compared with the conventional LED chip. This improvement can be explained by both the additional current injection into the effective active layer of the LED by the SHRR structure and the reduction in optical absorption under the p-pad electrode.