Fig. 1. Schematic cross section structures of the vertical 4H-SiC (a) n-i-p APD and (b) p-i-n APD; (c) top view image of one fabricated APD.

Fig. 2. Simulated 2D electric field distribution of a beveled mesa SiC APD under avalanche breakdown voltage. The inset shows the one-dimensional (1D) electric field profile along the black line marked in the 2D electric field profile.

Fig. 3. I-V and gain-voltage curves of (a) the n-i-p APD and (b) the p-i-n APD; the insets show the enlarged gain regions of the two SiC APDs.

Fig. 4. Zero-bias spectral response curves of n-i-p and p-i-n APDs.

Fig. 5. (a) Typical avalanche voltage pulse signal under passive quenching circuit (the inset shows the schematic diagram of passive quenching circuit), (b) the DCR versus normalized overbias curves, (c) the SPDE versus normalized overbias curves, and (d) SPDE versus DCR curves of the n-i-p and p-i-n APDs.

Fig. 6. Gain-voltage curves measured at 260, 280, and 300 nm illumination for (a) the n-i-p APD and (b) the p-i-n APD. (c) The variation of V_B as a function of UV illumination wavelength.

Fig. 7. Schematics of the carrier ionization process at different incident light wavelengths for (a) the n-i-p APD and (b) the p-i-n APD. The illumination wavelength varies from deep UV to near UV wavelength regions.