Choong Hun Lee

Efficiency Improvement of 630 nm AlGaInP Light-Emitting Diodes based on AlGaAs Bottom Window

Metal organic chemical vapor deposition (MOCVD) based aluminum gallium arsenide (AlGaAs) used as the bottom window (BW), which was inserted between the light-emitting diode (LED) structure and the absorbing substrate, has been proposed to improve the extraction efficiency of 630 nm AlGaInP LEDs. In an AlGaInP LED with this AlGaAs BW, enhanced light extraction efficiency was observed, as some of the light emitted from the active region to the absorbing substrate could pass out of the LED through the BW. In addition, it was found that a output power of 8 mW was obtained from an AlGaInP LED with both a BW and a distribution Bragg reflector (DBR), a nearly two fold improvement of over 4.2 mW that was obtained from a conventional one at an injection current of 80 mA.

Effects of Nanosized Ni Particle Structure on the Enhancement of Light Extraction from 600 nm AlGaInP Light-Emitting Diodes

This paper reports on the effect of Ni particle structures on the light extraction in 600 nm AlGaInP light-emitting diodes (LEDs). A Ni film was deposited on top of a gallium phosphide (GaP) layer and the surface texture was improved by an ammonia (NH3) plasma etching process into a chamber resulting in the formation of Ni particles with an average size of 10 nm. AlGaInP LED with the Ni particle shows an increase in the light extraction by 75% and a higher emission intensity with a percentage increase of 112.5% as compared with the conventional AlGaInP LEDs.

Synthesis of Few‐Layer Graphene Using DC PE‐CVD

Few layer graphene (FLG) had been successfully grown on polycrystalline Ni films or foils on a large scale using DC Plasma Enhanced Chemical Vapor Deposition (DC PE‐CVD) as a result of the Raman spectra drawn out of the sample. The size of graphene films is dependent on the area of the Ni film as well as the DC PE‐CVD chamber size. Synthesis time has an effect on the quality of graphene produced. However, further analysis and experiments must be pursued to further identify the optimum settings and conditions of producing better quality graphene. Applied plasma voltage on the other hand, had an influence on the minimization of defects in the graphene grown. It has also presented a method of producing a free standing PMMA/graphene membrane on a FeCl3(aq) solution which could then be transferred to a desired substrate.