Pulse-filling method is available as a method for directly obtaining capture cross-section of the trap level: σc.
In the capture process, the trap concentration of captured electrons changes exponentially with respect to the pulse width and is given by the following formula (A-13).
τc: capture time constant, tp: pulse width
Capture time constant: τc is obtained from formula (A-13) by measuring the amplitude (that is, trap concentration) in the capacitance transient with various pulse widths, also, the capture cross-section is calculated from formula (A-14).
Generally, as the carrier capture rate of a trap is much faster than the emission rate, a short pulse in the range of several 10 ns to 1 μs is required for this measurement.
In FT-1030, an option to use an external high-speed pulse generator is available.