Single fast-pulsed interruption of on state of amorphous threshold switch: I-V decay curve and trapped-carrier lifetime
The on state of an amorphous threshold switching device has been analyzed during fast voltage descent from the on voltage through the holding voltage to zero. The resulting I-V characteristics show an initial region of Ohmic behavior, a subsequent region of transitional properties, and ultimately a region of residual voltage ascribed to space-charge asymmetry. These data indicate 10 nsec as the time for formation of the blocked on state through redistribution of the mostly trapped space charge at the blocked on threshold. The subsequent decay of the blocked on state in about 100 nsec takes place as the electrons recombine at the edges of their distribution with holes that flow in through the contacts. The observed positive residual bias implies an initial influx of Coulomb-attracted holes which is the greater through the anode contact, and this is consistent with the reported narrowing of the formed region of the diode near this contact. These results support the model of the space-charge on state due to electrons.