Ionization energies and electron mobilities in phosphorus- and nitrogen-implanted 4H-silicon carbide

Comparisons are made between the carrier concentrations, ionization energies, and electron mobilities in 4H-SiC samples implanted with similar doses of nitrogen or phosphorus, and annealed at 1300 °C or 1700 °C for 10 min in argon. Ionization energies of 53 meV and 93 meV are measured from phosphorus-implanted 4H-SiC, and are assigned to the hexagonal and cubic lattice positions in 4H-SiC, respectively. The corresponding ionization energies for nitrogen-implanted 4H-SiC are 42 meV and 84 meV, respectively. Phosphorus is not activated to the same extent that nitrogen is, and the carrier concentrations are about a factor of five lower for phosphorus-implanted 4H-SiC annealed at 1300 °C than for nitrogen-implanted 4H-SiC annealed at the same temperature. A higher mobility measured from phosphorus-implanted 4H-SiC is observed, but is not sufficiently high to offset the lower carrier concentration of this material. For the doses considered in this study, the resistivity of nitrogen-implanted 4H-SiC is lower than the resistivity of phosphorus-implanted 4H-SiC following anneals at either 1300 °C or 1700 °C.