Al composition dependence of breakdown voltage in AlxGa1-xN Schottky rectifiers

Planar geometry, lateral Schottky rectifiers were fabricated on high resist ivity AlxGa1-xN (x = 0-0.25) epitaxial layers grown on sapphire substrates. The reverse breakdown voltages of unpassivated devices increased with Al c omposition, varying from 2.3 kV for GaN to 4.3 kV for Al0.25Ga0.75N. The re verse current-voltage (I-V) characteristics showed classical Shockley-Read- Hall recombination as the dominant mechanism, with I proportional to V-0.5. The reverse current density in all diodes was in the range 5-10 x 10(-6) A cm(-2) at 2 kV. The use of p(+) guard rings was effective in preventing pr emature edge breakdown and with optimum ring width increased V-B from 2.3 t o 3.1 kV in GaN diodes. (C) 2000 American Institute of Physics. [S0003-6951 (00)00813-5].