Enhancement of (In,Ga)N light-emitting diode performance by laser liftoff and transfer from sapphire to silicon

(In,Ga)N light-emitting diodes (LEDs) fabricated on a sapphire growth substrate were successfully integrated onto Si substrates by a double-transfer technique using excimer laser liftoff and Pd-In transient-liquid-phase bonding. This transfer method resulted in a bonded LED heterostructure with the same orientation (p-side up) as the heterostructure before transfer from the sapphire growth substrate. Such a layer transfer approach enables a top and backside contact metallization scheme that reduces device series resistance, current crowding, and top electrode coverage area. Enhancement of the performance of the transferred LEDs was found in terms of the threshold voltage (at 20 mA) and the electroluminescence output from the front surface.