Leakage and trapping characteristics in Au-free AlGaN/GaN Schottky barrier diodes fabricated on C-doped buffer layers

We investigate the DC and dynamic characteristics of AlGaN/GaN Schottky barrier diodes (SBDs) and the diodes with a gated edge termination (GET-SBD) fabricated on unintentional doped (UID) and carbon-doped AlGaN buffers. The off-state characteristics of diodes fabricated on UID buffer are dominated by buffer leakage and buffer breakdown voltage (BV) at higher reverse voltage ( larger than 300 V). An improvement in diode leakage and BV can be obtained by fabricating the GET-SBDs on C-doped buffers. A pronounced degradation of the AlGaN/GaN SBDs and GET-SBDs on carbon-doped buffers was observed by dynamic pulsed characterization. This dynamic degradation causes a clear forward current reduction for the AlGaN/GaN GET-SBDs. From combined off-state stress and current transient measurements on AlGaN/GaN SBDs, the collapsed current is recoverable and the degradation is due to a temporary trapping mechanism occurring in the buffer. A distinct trap level of 0.57 eV from trap spectra has been extracted for the diode fabricated on C-doped buffer, and the value was implemented in a TCAD simulator. The simulated results confirm a bulk trapping in the buffer layer for the SBD and show an additional trapping region in the GET-SBD architecture.