Investigation of Trap States and Reverse Leakage in Fully-Vertical GaN Schottky Barrier Diodes with Laser Lift-Off Substrate

Lase lift-off (LLO) substrate technology is a promising solution for realizing fully vertical GaN devices based on foreign substrates. By performing deep-level transient spectroscopy (DLTS) experiments and temperature-dependent leakage current characterizations, this work investigates the trap states and leakage mechanisms of fully-vertical GaN Schottky barrier diodes (SBDs) based on LLO substrate, laser annealing and N-implantation termination. By fitting the DLTS spectral signal, the energy levels of the two electron trap states are determined to be
$E_{C}$
- 0.6 e V and
$E_{C}$
- 0.21 eV respectively, which should originate from the intrinsic traps in GaN epitaxy rather than being introduced by the LLO process. Furthermore, the leakage currents of the device are found to be dominated by Poole-Frenkel emission (PFE, < 35 V), variable range hopping (VRH, 35 ~ 100 V) and trap-assisted tunneling (TAT, > 100 V), respectively, as the bias voltage increases. These results provide important new insights into the implementation of laser lift-off technology in GaN-based power devices.