Reliably determining the densities and energy levels of deep-level dominant acceptors in heavily doped wide-band-gap semiconductors has been a topic of recent discussion. In these discussions, the focus is on both Hall scattering factors for holes and distribution functions for acceptors. Mg acceptor levels in 4H-SiC seem to be deep, and so here the electrical properties of Mg-implanted 4H-SiC layers are studied by measuring Hall effects. The obtained Hall scattering factors are not reliable because they drop to less than 0.5 at high measurement temperatures. Moreover, the Fermi–Dirac distribution function is unsuitable for examining Mg acceptors because the obtained acceptor density is much higher than the concentration of implanted Mg atoms. However, by using a distribution function that includes the influence of the excited states of a deep-level acceptor, the density and energy level of Mg acceptors can be reliably determined.

Because Al and B (elements of III group) in SiC are deep-level acceptors and these acceptors cannot reduce the resistivity of p-type SiC very much, Mg (element of II group) that may emit two holes into the valence band is investigated. A p-type 4H-SiC layer is obtained by 1800 °C annealing of the Mg-implanted layer, not by 1600 and 1700 °C annealing. It is found that a Mg acceptor level in 4H-SiC is too deep to determine the reliable density and energy level of the Mg acceptor using the frequently-used occupation probability, i.e., the Fermi-Dirac distribution function. Using the distribution function including the influence of the excited states of the Mg acceptor, therefore, its density and energy level can be determined to be approximately 1×1019cm-3and 0.6 eV, respectively. Judging from the Mg implantation condition, the obtained values are considered to be reliable.

Because Al and B (elements of group III) in SiC are acceptors with deep energy levels and these acceptors cannot reduce the resistivity of p-type SiC very much, Mg (an element of group II) that may emit two holes into the valence band is investigated. Annealing at 1800• C makes a Mg-implanted layer p-type. It is found that an Mg acceptor level in 4H-SiC is too deep to reliably determine the density and energy level of the Mg acceptor using the frequently used occupation probability, i.e., the FermiDirac distribution function. Using the distribution function that accounts for the inuence of the excited states of a deep-level acceptor, the density and energy level of Mg acceptors can be determined to be approximately 1 × 10 19 cm −3 and 0.6 eV, respectively. These values are considered to be reliable because they agree well with the Mg implantation condition.