Wafer bonding for high-brightness light-emitting diodes via indium tin oxide intermediate layers

A direct wafer-bonding technique has been used to fabricate high-brightness light emitting diodes (LEDs). However, bonding processes were usually performed at elevated temperatures, possibly causing degradation in the quality of the LED structure. In addition to this, misorientation between the two bonded wafers may have caused defects between the wafers. In this study, these two problems were solved by bonding the InGaP/GaAs and GaAs wafers with an indium tin oxide (ITO) polycrystalline film at temperatures below 650 °C. It was found that the bonding occurred mainly through the In transport from the InGaP to ITO, and that the electrical resistance decreased with the bonding temperature.