Analysis of the I–V characteristics of Al/4H-SiC Schottky diodes

The capability of silicon carbide in general to operate at high temperatures, and the fact that the electron mobility of the 4H-SiC polytype is twice that of the 6H polytype, has led to significant interest in 4H-SiC devices. Experimental data for Al/4H-SiC Schottky diodes is limited, and in this article we present forward and reverse I–V characteristics measured over a temperature range of 298–378 K. An analysis of the results shows that the charge transport mechanism is dominated by thermionic emission at forward biases less than 0.3 V, and series resistance at forward biases greater than 0.9 V. However, for a forward bias in the range of 0.3–0.9 V, we found the data fitted the space-charge-limited emission model. The competing mechanisms of thermionic emission and space-charge-limited emission lead to nonideal I–V characteristics, resulting in an increase in measured ideality factor. Space-charge-limited currents are dependent on the trap distribution in the material, and the estimated trap density is 4.4×1015 cm−3 eV−1. In the reverse direction, the I–V curves follow Bardeen’s model for metal–semiconductor contacts with an interfacial layer. Comparison with results published on 6H-SiC Schottky devices shows no significant differences, and our data falls within the spread found in the literature for all SiC results.