Picosecond range switching of a GaAs avalanche transistor due to bulk carrier generation by avalanching Gunn domains

Abstract

Superfast high current switching of a GaAs-based JBT in the avalanche mode has been achieved experimentally for the first time. A very fast reduction in the voltage across the transistor was observed (~ 200-300 ps) and the amplitude of the current pulses ranged from 2 to 130 A depending on the load resistance. It was observed experimentally that the switching occurs in a number of synchronized current channels with a characteristic diameter of ≤ 10 microns. A 1D simulation code was developed and the switching transient for a single channel was simulated, with the external circuit incorporated into the simulations. Photon-assisted carrier transport and negative differential electron mobility were taken into account in the theoretical model. The former does not play an appreciable role in the 1D switching transient, although the latter determines superfast switching at extreme current densities (> 1 MA/cm 2 ). Superfast switching occurs due to the appearance of a number of Gunn domains at any instant (up to ~ 20 domains across a collector region ~30 microns in thickness). These domains of huge amplitude (up to ~700 kV/cm) are moving towards the cathode and give rise to extremely high ionization rates across the volume of the channel in the n 0 collector region. The simulations provide a fairly reliable interpretation of the experimentally observed switching time, which is shorter than that in Si avalanche transistors by a factor of ~15. The new device is fairly attractive, e.g. for feeding pulsed laser diodes when the current rise time should be shorter than the lasing delay.

Investigation on the surface flashover of high gain SI‐GaAs PCSS

“…The width of such domain is expressed as From this equation, we can derive Based on the above equation, the field of the head domain is calculated, E 1 is the field outside of the high field domain and E 2 is the maximum field in the high field domain. For GaAs ɛ = 1.17 × 10 −10 C 2 N −1 m −2 , the width of this domain is 0.1 pm; n is the average carrier intensity in the bulk of switches. In general, the intensity of photogenerated carriers is more than 10 18 /cm 3 .From the second equation, we can calculate the field at the head of the domain as 10 3 kV/cm and which is far more than the avalanche breakdown threshold 250 kV/cm.…”

“…Based on the above equation, the field of the head domain is calculated, E 1 is the field outside of the high field domain and E 2 is the maximum field in the high field domain. For GaAs ɛ = 1.17 × 10 −10 C 2 N −1 m −2 , the width of this domain is 0.1 pm; n is the average carrier intensity in the bulk of switches. In general, the intensity of photogenerated carriers is more than 10 18 /cm 3 .…”