Microwave Annealing of High Dose Al+-implanted 4H-SiC: Towards Device Fabrication

High-purity semi-insulating 8 degrees off-axis aOE (c) 0001 > 4H-SiC was implanted with Al+ at different doses and energies to obtain a dopant concentration in the range of 5 x 10(19)-5 x 10(20) cm(-3). A custom-made microwave heating system was employed for post-implantation annealing at 2,000 A degrees C for 30 s. Sheet resistance and Hall-effect measurements were performed in the temperature range of 150-700 K. At room temperature, for the highest Al concentration, a minimum resistivity of 3 x 10(-2) Omega cm was obtained, whereas for the lowest Al concentration, the measured resistivity value was 4 x 10(-1) Omega cm. The onset of impurity band conduction was observed at around room temperature for the samples implanted with Al concentrations a parts per thousand yen3 x 10(20) cm(-3). Vertical p (+)-i-n diodes whose anodes were made by 1.5 x 10(20) cm(-3) Al+ implantation and 2,000 A degrees C/30 s microwave annealing showed exponential forward current-voltage characteristics with two different ideality factors under low current injection. A crossover point of the temperature coefficient of the diode resistance, from negative to positive values, was observed when the forward current entered the ohmic regime.