Comparison Between Epitaxial and Implanted Aluminum-Doped 4H-SiC

A comparison of p-type 4H-SiC with in situ doping of Al during epitaxial growth and with Al doping by implantation is studied here. Four-point van der Pauw samples are prepared, and resistivity and Hall measurements are carried out. SiC with in situ Al doping shows lower resistivity and a lower temperature coefficient than Al-implanted samples. Hall measurements reveal higher carrier concentrations and higher mobility for the in situ Al-doped sample at all temperatures. Extraction of the dopant ionization energy is obtained from the carrier concentration versus temperature and modeled using a two-level charge neutrality equation. The in situ-doped epitaxial sample shows only one ionization energy (230 meV), whereas the implanted sample shows an additional deep ionization energy level (350 meV). In the implanted sample, the activated carriers are distributed into two energy levels. The deep states with which some of the carriers are associated may be defect complexes and have a similar energy level to carbon-related D_I defects, reported by others.