Stress analysis of transferred thin-GaN LED by Au-Si wafer bonding

Abstract

Nowadays, the high power GaN-based LED has attracted serious attention for the lighting application. One of key issues for high power GaN-base LED to achieve sufficient lighting efficiency over the traditional light sources, such as, white incandescent and halogen light bulb is the efficiency of heat dissipation. Typically, GaN epi-layer is grown on sapphire substrates. The poor thermal conductivity of sapphire substrate has been identified to be the main limitation for the application of high power GaN LED. To improve the heat dissipation and lighting efficiency, we report a thin GaN structure by using Au-Si wafer bonding and Laser lift-off (LLO) technique. The GaN wafer was first deposited with a Au bonding layer and bonded onto a good thermal conduction substrate, i.e., heavy-doped Si. Then, 248nm KrF excimer Laser was used to strip the original sapphire substrate. To assure a successful GaN epi-layer transferring, Raman spectrum on the transferred GaN layer was performed and the result shows no quality change in the transferred GaN layer. In this work, we also fabricated the vertical LED devices on the transferred GaN epi-layer. Therefore, L-I-V result was obtained which will be presented in this talk. Moreover, we will discuss the effects and advantages of Au-Si bonding on the efficiency of lighting.

Temperature and thermal characteristics of InGaN/GaN vertical light-emitting diodes on electroplated copper

“…For VLEDs, a laser lift-off (LLO) process has been often used to remove the sapphire substrate from the GaN epitaxial layer. The wafer-bonding method may increase the contact resistance and cause a thermal stress during the heat treatment for soldering [13]. Alternatively, the electroplating method can be used to produce metals or metal alloys [14,15].…”