The effects of sapphire substrates processes to the LED efficiency

Abstract

We investigate the relation between the thickness of sapphire substrates and the extraction efficiency of LED. The increasing about 5% was observed in the simulations and experiments when the sapphire thickness changed from 100um to 200um. But the output power increasing is inconspicuous when the thickness is more than 200um. The structure on bottom face of sapphire substrates can enhance the extraction efficiency of GaN-based LED, too. The difference of output power between the flip-chip LED with smooth bottom surface and the LED with roughness bottom surface is about 50%, where only a common sapphire grinding process is used. But for those LEDs grown on patterned sapphire substrate the difference is only about 10%. Another kind of periodic pattern on the bottom of sapphire is fabricated by the dry etch method, and the output of the back-etched LEDs is improved about 50% than a common case.

Electrochemical Potentiostatic Activation for the Improvement of 270 nm AlGaN-Based UV-C Light-Emitting Diodes

“…The basic flip chip processing technology has been used in this study due to its excellent thermal conductivity. 19 Following the experimental design, the size of the UV LED chips was manufactured with the width × length of 1,250 μm × 1140 μm. Its bottom surface was deposited with a 3 μm-thickness AuSn layer and the ratio of Au:Sn was 80%:20% for the subsequent bonding process.…”