High-voltage subnanosecond avalanche sharpening diodes: A comparative study of silicon and gallium arsenide structures

Subnanosecond avalanche switching of dynamically overvoltaged diodes is known to occur for both Si and GaAs diodes. Here we present a novel comparative study of Si and GaAs structures. Original experimental setup that allows measuring current and voltage on the diode simultaneously and independently has been used for measurements. Si p
⁺
nn
⁺
and p
⁺
pnn
⁺
and GaAs p
⁺
nn
⁺
structures with similar geometrical parameters and stationary breakdown voltage ~1 kV have been investigated. All devices under study trigger at ~2 kV and are capable of forming a voltage ramp with kilovolt amplitude and 100-ps risetime. We found a drastic difference between Si p
⁺
nn
⁺
and p
⁺
pnn
⁺
relatively low residual voltage V
_res
~150 V has been observed only for p
⁺
nn
⁺
structures whereas for p
⁺
pnn
⁺
structures V
_res
~1 kV. The difference between Si and GaAs structures is much more dramatic: after 100-ps avalanche switching GaAs diode remains in high conducting state as long as the applied voltage pulse lasts. Within the same time of 2 ns the reference Si diode fully recovers the blocking capability. Next, the residual voltage on GaAs diode does not exceed several dozen volts. The discovered effect resembles the well-know lock-on effect in optically activated switches.