Temperature dependence and current transport mechanisms in Al_xGa_1-xN Schottky rectifiers

GaN and Al_0.25Ga_0.75N lateral Schottky rectifiers were fabricated either with (GAN) or without (AlGaN) edge termination. The reverse breakdown voltage V_B (3.1 kV for GaN with both p⁺ guard rings and metal overlap edge terminations; 4.3 kV for Al_0.25Ga_0.75N without edge termination) displayed a negative temperature coefficient of-6.0 ± 0.4 V.K^-1 for both types of rectifiers. The reverse current originated from contact periphery leakage at moderate bias, while the forward turn-on voltage at a current density of 100A·cm^-2 was ∼5 V for GaN and ∼7.5 V for AlGaN. The on-state resistances, R_ON were 0.13 Ωcm² for GaN and 2.3 Ωcm² for AlGaN, producing figures-or-merit (V_RB)²/R_ON of 73.9 and 8.2 MW.cm^-2, respectively. The activation energy of the reverse leakage was 0.13 eV at moderate bias.