High-voltage 4$H$-SiC based avalanche diodes with a negative beve

High-voltage 4$H$-SiC based avalanche $p^+$–$p$–$n_0$–$n^+$-diodes were fabricated. The diodes were designed as mesa- structures with gentle-slope walls forming the bevel of negative type. For negative beveling, selective dry etch process of SiC with a photo-resistive masking pad having a form of a sharp wedge at the edge was successfully used. The mesa's area and height are 1 mm$^2$ and 3.6 $\mu$m (which is slighly greater than the depth of the $p$–$n_0$-junction – 3 $\mu$m), respectively; the angle of the beveled wall is about 5 degrees. The I–V characteristics of fabricated diodes were measured. At forward current of 10 A, the differential resistance and voltage drop were measured to be 0.35 Ohm and 6.5 V, respectively. In reverse direction, the diodes demonstrated a sharp breakdown at voltages ranging from 1420 to 1500 V. By using a TCAD-simulation, the reverse I–V characteristic was caculated for an ideal one-dimensional diode possessing the same structure parameters. The avalanche breakdown voltage was calculated to be 1450 V. It means that the achieved efficience of junction termination is close to 100%. The pulsed reverse I–V characteristics was measured. In avalanche breakdown regime, the differential resistance was measured to be about 3 Ohm which indicates that the avalanche current is uniformly distributed within the diode area. The diodes can withstand single current pulses of at least 10 A in amplitude (current density of 10$^3$ A/cm$^2$) and 1.2 $\mu$s in time (avalanche energy is 9 mJ).