2nd PUC Physics semiconductor electronics chapter is an introduction to a to a whole new world of physics. In semiconductor electronics we will discover the devices which exhibit special properties of electronic devices that conductors and insulators fail to exhibit. 2nd PUC physics Semiconductor electronics will start with the basic understanding of semiconductor devices and materials, where we will further advance into studying the simple circuits made of semiconductor materials. 2nd PUC Physics Semiconductor electronics will also glance into the digital world where the students will be studying the basic logic used in the digital electronic devices. By the end of the chapter students will be able to look through the application of semiconductor devices and their commercial usage.


Classification of Metals, Conductors and Semiconductor 
Intrinsic Semiconductor 
Extrinsic Semiconductor 
p-n Junction 
Semiconductor Diode 
Application of Junction Diode as a Rectifier 
Special Purpose p-n junction Diodes 
Digital Electronics and Logic Gates 
Integrated Circuits 


What is semiconductor electronics?

Semiconductor Electronics is the branch of physics and technology that deals with the design of circuits using semiconductor devices.

What are Semiconductors?

Semiconductors are the basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc. Semiconductor is a substance which has conductivity between conductors and insulators.

Properties of semiconductors:

  • They have resistivity less than insulators and more than that of conductors.
  • Resistance of a semiconductor is inversely proportional to the temperature
  • When suitable metallic impurity is added to semiconductors, its current conducting properties change appreciably.

Types of semiconductors:

  • Intrinsic semiconductors: Semiconductors which are pure chemically, or who do not have any impurities added are called as intrinsic semiconductors. The number of electrons and holes is therefore determined by the properties of the material itself instead of the amount of impurities.
  • Extrinsic semiconductors: When a small amount, say, a few parts per million (ppm), of a suitable impurity is added to the pure semiconductor, the conductivity of the semiconductor is increased manifold. Such materials are known as extrinsic semiconductors or impurity semiconductors.

p-n junction in semiconductor devices:

  • p-n junction is the ‘key’ to all semiconductor devices. When such a junction is made, a ‘depletion layer’ is formed consisting of immobile ion-cores devoid of their electrons or holes. This is responsible for a junction potential barrier
  • By changing the external applied voltage, junction barriers can be changed. In forward bias (n-side is connected to negative terminal of the battery and p-side is connected to the positive), the barrier is decreased while the barrier increases in reverse bias. Hence, forward bias current is more (mA) while it is very small (µA) in a p-n junction diode.
  • p-n junctions have also been used to obtain many photonic or optoelectronic devices where one of the participating entity is ‘photon’:
(a) Photodiodes in which photon excitation results in a change of reverse saturation current which helps us to measure light intensity (b) Solar cells which convert photon energy into electricity (c) Light Emitting Diode and Diode Laser in which electron excitation by a bias voltage results in the generation of light.

Semiconductor diodes:

A semiconductor diode is basically a p-n junction with metallic contacts provided at the ends for the application of an external voltage. It is a two terminal device. There are some special purpose diodes as follows:
  • Zener diode is one such special purpose diode. In reverse bias, after a certain voltage, the current suddenly increases (breakdown voltage) in a Zener­­ diode. This property has been used to obtain voltage regulation.
  • A junction transistor has three doped regions forming two p-n junctions between them. Obviously, there are two types of transistors