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 1.5x10(20) cm(-3) and 5.0x10(20) cm(-3) were produced by the combination of high-dose (1.0 and 3.3x10(16) cm(-2)), multienergy (50-450 keV) Al+ ion implantation of 6H-SiC at -130 °C, ion-beam-induced crystallization with 500 keV, 5x10(15) Si+ cm(-2) at 500 °C and subsequent furnace annealing at 1500 °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 °C is enhanced by more than one order of magnitude from 9.0x10(17) cm(-3) to 1.6x10(19) cm(-3) in the case of 1.5x10(20) Al cm(-3) and from 6.1x10(18) cm(-3) to 8.0x10(19) cm(-3) in the case of 5.0x10(20) 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. (C) 2002 American Institute of Physics.