ELECTRIC BREAKDOWN IN GAN P-N-JUNCTIONS

Electric breakdown in GaN p-n junctions was investigated. GaN p(+)-p-n (+) structures were grown on 6H-SiC substrates by metalorganic chemica l vapor deposition. Mg and Si were used as dopants. Mesa structures we re fabricated by reactive ion etching. Capacitance-voltage measurement s showed that the p-n junctions were linearly graded. The impurity gra dient in the p-n junctions ranged from 2 x 10(22) to 2 x 10(23) cm(-4) . Reverse current-voltage characteristics of the p-n junctions were st udied in the temperature range from 200 to 600 K. The diodes exhibited abrupt breakdown at a reverse voltage of 40-150 V. The breakdown had a microplasmic nature. The strength of the electric breakdown field in the p-n junctions depended on the impurity gradient and was measured to be from 1.5 to 3 MV/cm. It was found that the breakdown voltage inc reases with temperature. The temperature coefficient of the breakdown voltage was similar to 2 x 10(-2) V/K. (C) 1996 American Institute of Physics.