Bonded GaN-Si pn Heterojunctions Fabricated Using Transferred GaN Membranes

Abstract The ability to transfer and bond GaN membranes can enable new devices and new ways to optimize performance. Here, we demonstrate fabrication of GaN-Si pn diodes using van der Waals (vdW) lift-off and bonding of GaN membranes and assess the critical processing and interface challenges with this approach. Freestanding n-GaN layers were produced by epitaxial lift-off from sp 2 -bonded boron nitride-sapphire templates followed by direct bonding to p + -Si substrates. Fabricated diodes exhibited high on/off current ratios up to 8 × 10 7 , ideality factors of 1.8, and low series resistance. Annealing bonded heterojunctions at 400°C improved the ideality factor compared to as-bonded devices. Transmission electron microscope imaging revealed a well-bonded interface with only a 2-nm-thick oxide interlayer. Current-voltage analysis and device simulations indicated that the observed transport mechanism is due to recombination at defects in the GaN near the bonded interface. These results pave the way for a better understanding of bonded GaN junctions and how to improve their quality.