Affiliation: | 1.Department of Electrical and Computer Engineering,George Mason University,Fairfax,USA;2.LT Technologies,Fairfax,USA;3.CNISM - Dipartimento di Fisica,Università di Parma,Parma,Italy;4.CNR-IMM of Bologna,Bologna,Italy |
Abstract: | High-purity semi-insulating 8° off-axis 〈0001〉 4H-SiC was implanted with Al+ at different doses and energies to obtain a dopant concentration in the range of 5 × 1019–5 × 1020 cm?3. A custom-made microwave heating system was employed for post-implantation annealing at 2,000 °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 × 10?2 Ω cm was obtained, whereas for the lowest Al concentration, the measured resistivity value was 4 × 10?1 Ω cm. The onset of impurity band conduction was observed at around room temperature for the samples implanted with Al concentrations ≥3 × 1020 cm?3. Vertical p +-i-n diodes whose anodes were made by 1.5 × 1020 cm?3 Al+ implantation and 2,000 °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. |