Abstract
The free hole density and low-field mobility of aluminum-doped 4H-SiC were investigated in the temperature range of 100-900 K, both, experimentally and theoretically. Experimental data for implanted p-type 4H-SiC were compared with theoretical calculations using parameters determined for high-quality epitaxial layers. The deformation potential for intra- and intervalley scattering by acoustic phonons and the effective coupling constant for intra- and intervalley scattering by nonpolar optical phonons were determined. The detailed analysis of the implanted layers with aluminum-targeted concentration ranging from 3.33x10(18) to 10(21) cm(-3) shows that (i) about half of the implanted atoms are electrically active in the SiC lattice, (ii) a systematic compensation of about 10% of the doping level is induced by the implantation process, (iii) two different ionization energies for the aluminum atoms have to be used. Their origin is discussed in terms of inequivalent hexagonal and cubic lattice sites. Finally, the doping dependence of the ionization ratio and Hall mobility are given for non- and weakly (10%) compensated material at 292 K. The maximum achievable mobility for low-doped material in p-type 4H-SiC is shown to be 93 cm(2)/V s at room temperature.