Demonstration of Vertical GaN Schottky Barrier Diode With Robust Electrothermal Ruggedness and Fast Switching Capability by Eutectic Bonding and Laser Lift-Off Techniques

In this letter, we have successfully transferred the 4-inch crack-free GaN films from sapphire substrate to conductive silicon wafer by employing eutectic bonding and laser lift-off (LLO) techniques. The resultant 1-mm2 fully-vertical GaN Schottky barrier diodes (SBDs) exhibit a high current swing of 109, a low ideality factor of 1.03 and a high forward current of 10 A. Meanwhile, a decent breakdown voltage of 312 V is achieved, which is over 3 times higher than that of control device without performing epitaxial lift-off. Most importantly, such rectifiers show significantly enhanced electrothermal ruggedness, achieving a high surge-current density of 2.6 kA/cm2 and a low thermal resistance of 0.77 K·cm2/W. In addition, the excellent power rectification capability with a low reverse recovery time of 14 ns is obtained under high-speed switching condition with a high current ramp rate ( $di/dt$ ) of 275 ${\mathrm {A/\mu s}}$ , implying the desired functionality of the LLO-vertical device architecture. These results thus present the great potentials of the substrate-transferred GaN SBDs for high-power and high-efficiency applications.