Ultrahigh field multiple Gunn domains as the physical reason for superfast (picosecond range) switching of a bipolar GaAs transistor

Abstract

The superfast (picosecond range) high-current switching observed recently in a GaAs junction bipolar transistor is explained by practically homogeneous carrier generation in the volume of the switching channels by a moving train of avalanching Gunn domains of large amplitude. The very fast (∼200ps) reduction in the collector voltage is determined by shrinkage of each domain, provided the negative electron mobility in ultrahigh electric fields is taken into account and current filamentation takes place. The results of one-dimensional simulations show good quantitative agreement with experimental voltage and current wave forms when the simulated switching area is equal to the summed areas of the filaments observed in the experiment.

Terahertz Emission from Collapsing Field Domains during Switching of a Gallium Arsenide Bipolar Transistor

“…Relatively weak impact ionization in Gunn domains may complicate the effect due to presence of holes, and cause current filamentation [2,3]. Powerfully ionizing multiple domains with very unusual parameters and temporal evolution were recently predicted in transient simulations of superfast switching in an n -p-n 0 -n transistor structure in which copious electron injection takes place into a high-voltage biased (depleted) layer of n-type gallium arsenide [4,5]. Current filamentation is intrinsic to this regime [4].…”

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

“…For decades the lock-on effect was a puzzle. The key finding that has helped to explain such anomalous dynamics is the discovery of collapsing high-field domains that spontaneously appear in electronhole plasma due to negative differential electron mobility in GaAs [19]- [21]. These domains were originally predicted as a mechanism that explains picosecond-range switching and terahertz emission in GaAs avalanche transistors [19], [20].…”

“…The key finding that has helped to explain such anomalous dynamics is the discovery of collapsing high-field domains that spontaneously appear in electronhole plasma due to negative differential electron mobility in GaAs [19]- [21]. These domains were originally predicted as a mechanism that explains picosecond-range switching and terahertz emission in GaAs avalanche transistors [19], [20]. The mechanism that initiates the instability of the spatially uniform current flow is essentially the same as that for the well-known Gunn effect and is related to negative differential conductivity [19]- [21].…”

“…These domains were originally predicted as a mechanism that explains picosecond-range switching and terahertz emission in GaAs avalanche transistors [19], [20]. The mechanism that initiates the instability of the spatially uniform current flow is essentially the same as that for the well-known Gunn effect and is related to negative differential conductivity [19]- [21]. However, the shape and spatiotemporal dynamics of collapsing domains turn out to be very different from the conventional monopolar Gunn effect [22] as well as from the early analytical description of bipolar Gunn domains [23].…”

Transmission Subterahertz Imaging Utilizing Milliwatt-Range Nanosecond Pulses from Miniature, Collapsing-Domain-Based Avalanche Source

“…The fi gure represents data of Ref. [ 24 ] width of a few microns, only one sort of carriers (electrons) is presented and no impact ionization manifests itself. In contrary, in our case multiple fi eld domains are generated, which number varies from a few to ~20 during the transient; the ionization threshold is exceeded several times and causes extremely powerful impact ionization; both electrons and holes are presented forming plasma between the domains; drastic domain shrinkage causes very fast voltage reduction across the structure and even complete domain disappearance [ 27 ].…”