Superfast high-current switching of GaAs avalanche transistor

A GaAs homojunction bipolar transistor has been developed and tested in high-current avalanche mode. The voltage across the transistor dropped from ∼300 to ∼60 V during a transient time of ∼200 ps. Current pulses of amplitude 120 A were measured across the low-ohmic load and the current risetime of ∼2 ns was limited by the parasitic inductance of the circuit. A number of switching channels of ∼10 µm in diameter were directly observed in the experiment. The switching time is shorter by a factor of ∼15 than that achievable with Si avalanche transistors.