High-energy (MeV) Al and B ion implantations into 4H-SiC and fabrication of pin diodes

High-energy (MeV) implantation of Al+ or B+ into 4H-SiC epilayers has been investigated. A 3 μm deep pn junction was formed by multiple-step Al+ or B+ implantation with implantation energies up to 6.2 or 3.4 MeV, respectively. Rutherford backscattering channeling and cross-sectional transmission electron microscopy analyses have revealed residual damages in the implanted layers even after high-temperature annealing at 1600–1800 °C. Nevertheless, high electrical activation ratios over 90% have been achieved for both Al+- and B+-implanted layers by annealing at 1800 °C. Mesa pin diodes with a 15-μm-thick i layer formed by MeV implantation have exhibited high breakdown voltages of 2860–3080 V. The reverse characteristics of diodes have been substantially improved by increasing annealing temperature up to 1800 °C. The diode performance is discussed with the results of deep level analyses near the junctions.