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Description
In this work, we study boron-induced defects in 4H-SiC Schottky barrier diodes (SBDs) by employing minority carrier transient spectroscopy (MCTS). Additional electrical characterization was performed using temperature-dependent current-voltage (I–V), capacitance-voltage (C–V), and deep-level transient spectroscopy (DLTS) measurements to determine the effects of unintentionally incorporated boron on the steady-state electrical performance of n-type 4H-SiC semitransparent Schottky barrier diodes. The SBDs were fabricated on lightly nitrogen-doped 4H-SiC epitaxial layers with a thickness of approximately 25 µm, while semi-transparent nickel films were evaporated with a thickness of 15 nm to form a Schottky barrier diode. The MCTS study identified that the introduction of boron resulted in at least two deep-level defects identified as shallow boron (B) and deep boron (D-center). The activation energies for hole emissions for B and D-center are estimated as EV + 0.21 and EV + 0.60 eV, respectively. The concentrations of these defects were determined to reach values up to 1×10^15 cm−3. The boron concentration was found to be higher than the nitrogen-dominated net effective doping concentration of ~3 × 10^14 cm−3 determined from the room-temperature (RT) C-V measurements. Even though the boron concentration was extremely high, no discernable decline in the steady-state electrical properties of the n-type 4H-SiC SBDs was found.
