Short-Pulse Properties of the Gunn Diode

The pulsed I-V characteristics of a Gunn diode are measured under the test pulse durations from 18 ns to 50 μs. For the test, a Gunn diode fabricated at the Scientific-Research Institute of Semiconductor Devices (Russia, Tomsk) on an n
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-n-n
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GaAs epitaxial structure was chosen. We found that it is important to provide low internal resistance of the measurement system to prevent voltage skipping in the suprathreshold section of the I-V characteristic. The measurement system with an internal resistance of about 0.5 Ω and linear calibration of the measurement circuit has been developed. An increase in the threshold voltage with a decrease in the test pulse duration was observed. This effect is explained by the influence of the contacts' resistance in combination with the temperature dependence of the active area resistance. It is established that this effect also leads to a delay of the domain mode start. We found that the duration of the test pulse maximally affects the threshold current at the durations approximately equal to the thermal relaxation time of the active area (73 ns). Two components can be singled out in this dependence: the first component is associated with the self-heating of the crystal lattice of active area and the second one (the fastest process, 15 ns) is associated with the transfer of some electrons to the second valley in the hottest part of the active area. Registration of the last process probably can be used for diagnostics of the quality of the Gunn diode contacts.