Picosecond-Range Avalanche Switching of High-Voltage Diodes: Si Versus GaAs Structures

We present a comparative study of Si and GaAs high-voltage diodes operated in the delayed impact ionization breakdown mode. We use an experimental setup that allows measuring current and voltage on the diode simultaneously and independently during a 100-ps high-voltage switching transient. Si and GaAs structures with identical geometries and a stationary breakdown voltage of ~1 kV were investigated. All devices trigger at close to 2 kV and are capable of forming a voltage ramp with a kilovolt amplitude and a 100-ps rise time. We found that Si p
⁺
nn
⁺
and p
⁺
pnn
⁺
structures differ in residual voltage: a relatively low residual voltage Vres of 100-200 V was observed only for p±nn± structures, whereas for p
⁺
pnn
⁺
structures Vres is about 1 kV. We report observing the lock-on effect in GaAs structures: after 100-ps avalanche switching GaAs diodes remain in a high conducting state as long as the applied voltage pulse lasts, whereas within the same time of 2 ns reference Si diodes fully recover the blocking capability.