Isochronal annealing on n-type 4H-SiC epitaxial schottky barriers and investigation of defect levels by deep level transient spectroscopy

Abstract

Schottky barriers were fabricated on 50 µm thick ntype 4H-SiC epitaxial layers. The effective doping concentration was calculated from high frequency (1 MHz) capacitance-voltage (C-V) measurements and was found to be ~ 9x10 14 cm -3 . Using a thermionic emission model, an effective barrier height of 1.22 eV and an ideality factor of 1.6 were calculated from the room temperature forward current-voltage (I-V) characteristics. The barrier height was also calculated from the C-V measurements and was found to be slightly higher compared to that obtained from I-V measurements, which suggests a spatial variation of surface barrier height across the device surface area. Capacitance mode deep level transient spectroscopy (DLTS) in the temperature range 80 to 800 K revealed the presence of four electron traps located in the energy range of 0.17 -1.6 eV below the conduction band edge (E c ). Three deep level defects at E c -0.67 eV (Z 1/2 ), E c -1.04 eV (EH 5 ), and E c -1.67 eV (EH 6/7 ) are detected along with one shallow level defects at E c -0.17 eV (Ti(c)). The capture cross-sections and defect densities were studied systematically through DLTS measurements before and after isochronal annealing in the temperature range of 100 -800 K. Among different defects, Z 1/2 and EH 6/7 are found to be very stable in the entire isochronal annealing range. The defects' parameters are evaluated and correlated with previous studies.Index Terms-4H-SiC, epitaxial layers, Schottky barrier, defect levels, deep level transient spectroscopy, isochronal annealing.