Wafer bonding is being investigated as a means to integrate other materials and to combine micromachined structures with microelectronics. Researchers at the University of California, Berkeley, have used an epoxy bond for attaching a sap-phire wafer with a gallium-nitride (GaN) film to a silicon wafer. The sapphire wafer is bonded faced down to the silicon wafer. Short, high-intensity pulses from a laser scanned back and forth across the sapphire wafer separated theGaN from the sapphire. The GaN that remained attached to the silicon waferdid not have irregularities in the film [13].