pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 829-835

Published online October 30, 2020 https://doi.org/10.3938/NPSM.70.829

## Effect of Etch Depth and Etch Angle of Etched LEDs on the Light Extraction Efficiency

Kee Young KWON*, Jang Geun KI

Division of Electrical, Electronic and Control Engineering, Kongju National University, Cheonan 31080, Korea

Correspondence to:kky@kongju.ac.kr

Received: May 7, 2020; Revised: August 31, 2020; Accepted: September 2, 2020

### Abstract

The effects of electrode absorption in a TIP (truncated inverted pyramid) LED (light-emitting diode) and of the etch depth and the etch angle of an etched LED on the light extraction efficiency have been studied. TIP LED may have a 100\% light extraction efficiency if no loss occurs in the medium, but when absorption occurs at the electrode, the light extraction efficiency decreases rapidly and is highest when the height of the active region is located at the center of the two electrodes. In the case of the etched LED, when the etch depth exceeds 36% of the chip thickness, the effect of increasing the light escape cone becomes dominant. If the light absorption coefficient of the chip material is zero, the light extraction efficiency approaches 100% when the etch angle exceeds 20 degrees. Even for a loss of $\alpha$ = 5 [cm$^{-1}$] inside the chip, the effect of increasing the light escape cone becomes dominant when the etch angle exceeds 20 degrees.

Keywords: Etched LED, Etch depth, Etch angle, Light efficiency