Characterization of SiC Implanted with B or Al Using Thermal Admittance Spectroscopy

Abstract

AbstractWe have measured the thermal activation energies of electrically active defects in 4H- and 6H-SiC implanted with either Al or B ions, using Thermal Admittance Spectroscopy. The net acceptor concentrations were monitored using room temperature low frequency Capacitance-Voltage measurements. The substrates were n/n+ epilayers. The implantations plus annealing produced p-type layers that were acceptable for characterization. The specimens were annealed in Ar at 1600 ° C, after which Ni Schottky diodes were fabricated on the specimens. Annealing times were 5, 15, 30, and 60 min. In some of the specimens, a shallow level was found that did not correspond to known levels. As the annealing progressed, energy shifts were noted for some of the detected levels. In some specimens, the implanted p-type impurity and the n-type residual dopants in the substrate were simultaneously detected. Measurements of electrically active ptype species were compared to “control” specimens implanted with Ar. From this comparison, we conclude that at least one shallow donor level is introduced into the bandgap by the implantation process, and is not annealed out. The defects associated with the implantation may affect actual device performance of diodes by destabilizing the lattice occupation of the implanted dopant atoms (energy shift with annealing), and act as lifetime killers.