Paper Title
ENHANCING THE LIGHT-EXTRACTION EFFICIENCY IN GaInN LEDS USING GRADED-REFRACTIVE-INDEX (GRIN) PILLARS

Abstract
Abstract - The main goal of this research is to enhance light-extraction efficiency (LEE) in GaInN light-emitting diodes by absolutes cancellation of total internal reflection (TIR). The planar LEDs have total internal reflection that is originated by the high refractive index difference between the semiconductor of LED and surrounding medium (air). In this paper is to reduce the trap light inside the LED by controlling the refractive index with various composition of (TiO2)x(SiO2)1−x in GRIN LEDs consisting of eight dielectric layers. In addition, multilayer GRIN LEDs are simulated: the transmittance value with many layers is greater than LEDs with fewer layers. LED with high transmittance value also increases the value of LEE. The analytical simulations provided that the five-layer GRIN LED’s light-extraction efficiency remains 28.54% and 8.382 times the LEE of uncoated LEDs. The eight-layer GRIN LEE, which is 8.438 times the uncoated LED, obtains 28.73%. The LEE and emission surfaces in designs with more than five-layer do not change significantly than in five-layer design but these GRIN designs are made the remove TIR and these results are higher than the uncoated LEDs LEE. From the results, the multilayer GRIN LEDs enhanced the LEE via the transmittance and refractive index. Keywords - Dielectric layers, Refractive Index, Total internal reflection (TIR), Transmittance.