Fig. 1. Surface SEM images of GaN film (a) before and (b) after KOH etching.

Fig. 2. (Color online) (a) The schematic structure of N-polarity GaN-based SBD. (b) Surface OM image of a fabricated N-polarity GaN-based SBD.

Fig. 3. (Color online) J−V curves of SBD devices with different annealing times in (a) linear scale and (b) semilog scale. (c) lnI−V curve of the SBD device with an annealing time of 60 s.

Fig. 4. (Color online) (a) Ideal factor and SBH of SBD devices with different annealing times. (b) Rectification ratios at ±5 V of SBD devices with different annealing times.

Fig. 5. (Color online) J−V curves of SBD devices with different annealing temperatures in (a) linear scale and (b) semilog scale.

Fig. 6. (Color online) (a) Ideal factor and SBH of SBD devices with different annealing temperatures. (b) Rectification ratios at ±5 V of SBD devices with different annealing temperatures.

Fig. 7. (Color online) The relationship curves between N_SS and E_C−E_SS for SBD devices with different annealing (a) times and (b) temperatures. (c) C−V and 1/C²−V curves, (d) ln(I/ξ)−ξ^0.5 curves and (e) lnI−1/T curves of the SBD devices without and with annealing at 450 ℃ for 60 s. (f) ln(I/ξ²)−ξ⁻¹ curve of the SBD device with annealing at 450 ℃ for 60 s.

Fig. 8. (Color online) The energy band diagrams of Schottky contact region for SBD devices (a) without annealing and (b) with annealing at 450 ℃ for 60 s.

Table 0. Physical notations used in this work and corresponding physical names.

Table 0. Characterization of nominally undoped metal-polarity and N-polarity GaN.