Low-resistivity, p-type SiC layers produced by Al implantation and ion-beam-induced crystallization

Low-resistivity (<0.1 Ω cm), p-type SiC layers of about 500 nm width and targeted acceptor concentrations of 1.5x1020 cm-3 and 5.0x1020 cm-3 were produced by the combination of high-dose (1.0 and 3.3x1016 cm-2), multienergy (50-450 keV) Al+ ion implantation of 6H-SiC at -130 deg. C, ion-beam-induced crystallization with 500 keV, 5x1015 Si+ cm-2 at 500 deg. C and subsequent furnace annealing at 1500 deg. C for 10 min. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped, nanocrystalline layers were investigated by sheet resistance and Hall measurements in dependence on temperature and compared with results from single-crystalline reference samples. In comparison with the standard doping process, the hole concentration at 50 deg. C is enhanced by more than one order of magnitude from 9.0x1017 cm-3 to 1.6x1019 cm-3 in the case of 1.5x1020 Al cm-3 and from 6.1x1018 cm-3 to 8.0x1019 cm-3 in the case of 5.0x1020 Al cm-3, respectively. It can be speculated that the loss of active Al acceptors by precipitation is reduced in the nanocrystalline layers and, therefore, the critical concentration for the formation of an impurity band can be achieved