Basic Electronics (EC1101) Introduction to Semiconductors By: 1107_003 This document is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. You are free to use, distribute and modify it, including for commercial purposes, provided you acknowledge the source and share-alike. To view a copy of this license, visit https://creativecommons.org/licenses/

TOPICS TO BE COVERED Introduction Historical Background Physical Properties

LEARNING OBJECTIVE Students should be able to: List and relate important historical events related to semiconductors Explain the concept of unilateral conduction List the important properties associated with semiconductors

INTRODUCTION Semiconductors Unilateral conduction resistor p-n junction diode tap i i

HISTIRICAL BACKGROUND 1874 - unilateral conduction of crystals. 1939 - Germanium (Ge) diode 1947 - Germanium (Ge) transistor relatively easy to find, available in fairly large quantities, and easy to refine to obtain very high levels of purity.

INTRODUCTION 1954 - Silicon (Si) transistor less temperature sensitive, and it is available in abundance. early 1970’s - Gallium arsenide (GaAs) transistor GaAs transistor had speeds of operation up to five times that of Si.

PHYSICAL PROPERTIES Conductivity: Electrical conductivity is a measure of a material's ability to conduct an electric current. Temperature coefficient of resistance: Change in the resistance offered by a material to the flow of electrons through it changes with change in temperature. Property Material Metals Semiconductors Insulators Conductivity (σ) unit (S m −1 ) 10 2 - 10 8 10 5 - 10 −6 10 −11 - 10 −19 temperature coefficient Positive (PTC) Negative (NTC) (at v. high temp.)

Image Credits Image of tap: http://www.aliexpress.com/popular/kitchen-tap- parts.html

REFERENCES Wikipedia - https://en.wikipedia.org/wiki/Main_Page Electronic Devices & Circuit Theory (11e) by R. L. Boylestad & L. Nashelsky of Pearson Education Electronic Devices and Circuits (2e) by B. P. Singh & R. Singh