2-55
Unlike the pn-junction diode, the point-contact diode depends on the pressure of contact between a
point and a semiconductor crystal for its operation. Figure 2-51A and B, illustrate a point-contact diode.
One section of the diode consists of a small rectangular crystal of n-type silicon. A fine berylium-copper,
bronze-phosphor, or tungsten wire called the CATWHISKER presses against the crystal and forms the
other part of the diode. During the manufacture of the point contact diode, a relatively large current is
passed from the catwhisker to the silicon crystal. The result of this large current is the formation of a
small region of p-type material around the crystal in the vicinity of the point contact. Thus, a pn-junction
is formed which behaves in the same way as a normal pn-junction.
Figure 2-51A.—Point-contact diode. DIAGRAM.
Figure 2-51B.—Point-contact diode. P REGION AROUND POINT.
