Evaluating the Switching Efficiency of Avalanche S-Diodes in a High-Current Mode

The work compares the switching efficiency of avalanche S-diodes in 1-D drift-diffusion (DD) and hydrodynamic (HD) models. It investigates low-voltage S-diodes with a switching voltage of ${V} _{\text {S}}~\approx ~150$ –180 V operating in current pulse generation circuits with a pulse duration of 1.7 ns (base pulsewidth) and an amplitude of $\approx 30$ A. The residual ON-state voltages across S-diodes are attributed to such processes as recombination, ohmic conduction, and nonohmic conduction caused by the avalanche generation of carriers during the formation and movement of ionizing domains. The generation of ionizing domains makes the greatest contribution to switching losses, which require a certain voltage to be maintained on the S-diode. A HD approach was discovered to quantitatively describe the switching behavior for the most efficient S-diodes with a residual voltage of $0.24{V} _{\text {S}}$ . Low-efficiency S-diodes with a residual voltage of up to $0.48{V} _{\text {S}}$ are supposedly switched by small-diameter conducting channels (no more than $14.2~\mu $ m). Unlike the DD approach, the HD approach produces 2.5 times slower switching and a higher residual voltage in S-diodes, which are due to wider ionizing domains originated in conducting channels.