
543Microwave Diodes
illustrates the variation of avalanche breakdown voltages with impurity at a
p
+
-n junction for different semiconductors.
In view of the above description the devices which involve avalanche mul-
tiplication and transit time are referred to as avalanche transit time devices.
These include Read, IMPATT, TRAPATT and BARITT diodes.
13.6.1 Read Diodes
The Read diode is one of the avalanche transit time devices which involve
avalanche multiplication and transit time effect and may have n
+
-p-i-p
+
or
p
+
-n-i-n
+
structure.
13.6.1.1 Operation
Figure 13.34a shows an n
+
-p-i-p
+
reverse biased Read diode structure.
In this structu