High critical electric field of AlxGa1−xN p-i-n vertical conducting diodes on n-SiC substrates

We report the current-voltage characteristics of AlxGa1−xN (x=0–0.22) p-i-n vertical conducting diodes grown on n-SiC substrates by low-pressure metal organic vapor phase epitaxy. An increase in the breakdown voltage was experimentally demonstrated with increasing Al composition. The corresponding critical electric fields were calculated to be 2.4MV∕cm for GaN and 3.5MV∕cm for Al0.22Ga0.78N. The critical electric field is proportional to the band gap energy to a power of 2.5. The forward voltage drop also increases with increasing Al composition but it is still as low as 5.2V even in the case of the Al0.22Ga0.78N p-i-n diode.