High-Voltage 4H-SiC-Based Avalanche Diodes with a Negative Bevel

Abstract

High-voltage avalanche p⁺–p–n⁰–n⁺ diodes based on 4H–SiC are fabricated. The diodes are made in the form of mesa structures with flat side walls forming a negative bevel. The mesa structures are formed by the dry reactive ion etching of 4H-SiC through a wedge-shaped photoresist mask. The mesas have an area of 1 mm², a height of 3.6 μm (slightly exceeding the bedding depth of 3 μm of the p–n⁰ junction), and the angle of inclination of the side walls is ~5° from the plane of the p–n⁰ junction. The I–V characteristics of the manufactured diodes are measured. At a current of 10 A, the differential resistance of the diodes and the voltage drop in the forward direction are 0.35 Ω and 6.5 V, respectively. In the reverse direction, the diodes exhibit an abrupt breakdown at voltages from 1420 to 1500 V. Using TCAD simulation, the reverse I–V characteristic of an idealized one-dimensional diode with the same parameters of the structure as in real diodes is calculated. The calculated voltage of a one-dimensional avalanche breakdown diode (1450 V) falls within the measured value range; i.e., the efficiency of the negative bevel as a security circuit is close to 100%. The pulsed reverse I–V characteristics of diodes in the powerful-avalanche breakdown mode are measured: the differential resistance is ~3 Ω, which indicates that the avalanche breakdown is uniform in area. The diodes withstand without destruction avalanche-current pulses with an amplitude of at least 10 A (current density of 10³ A/cm²) and a duration of 1.2 μs (dissipated energy of 9 mJ).