Exam Question

Semiconductors are a class of materials with conductivity between that of metals and that of insulators. Silicon and germanium are the two most commonly used semiconductor materials. At absolute zero pure semiconductors behave as insulators as there are no free charge carriers to conduct electricity. As the semiconductor temperature increases, more charge carriers are produced and the conductivity increases.
Generally semiconductors Diodes are 2 layer semiconductor devices, they will only conduct in one direction. If a voltage is applied across a diode in the direction that will cause conduction it is said to be forward biased otherwise it is said to be reverse biased.
Advantages of semiconductor over thermionic devices are:
Low Power Consumption and longer life