
548 Microwave Engineering
where V
b
is the applied voltage, V
b
is the breakdown voltage and parameter
n varies between 3 and 6 for silicon. In the saturation process the satura-
tion velocity for carriers generally exists in all semiconductor devices. In p-n
junction the motion of carriers takes place with carrier drift velocity. This
velocity becomes constant under the inuence of E. The threshold value of E
for silicon is 10
4
V/m.
13.6.2.2 Construction
IMPATT diode illustrated in Figure 13.36a is a solid-state power device made
from a highly doped semiconductor layer. This is called n
+
layer. On this
layer another n
−
layer is deposited epi