
538 Microwave Engineering
13.5.5.2 Current Fluctuations
The uctuation of current is shown in Figure 13.30. This current waveform
was produced by applying a voltage pulse of 16 V amplitude and 10 ns dura-
tion to a specimen of n-type GaAs, 2.5 cm in length. Oscillation frequency
was 4.5 GHz. Lower trace had 2 ns/cm in the horizontal axis and 0.23 A/cm
in the vertical axis. Gunn found that the period of these oscillations was equal
to the transit time of electrons through the specimen, calculated from the
threshold current. Gunn also discovered that threshold electric eld E
th
varies
with length and type of material.
13.5.6 LSA Diode
As discuss