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Semiconductor Semiconductor device materials In modern consumer electronics, it would be more difficult to find a component or product without a semiconductor. Semiconductors play a major role in everything from extremely sophisticated medical equipment to the most inexpensive transistor radio.

Learning Objectives

After completing the topic, the student will be able to:

  • Understand and analyze band theory in solids.
  • Examine and discuss semiconductor doping.
  • Investigate, explore semiconductor diodes and its types and characteristics.
  • Discuss the working of transistor and its configuration.
  • Identify amplifying action of transistor.
  • Appreciate and explore transistor as an oscillator.
  • Examine and discuss the working and application of FET and MOSFET.
  • Understand the logic gates which are the building blocks of digital electronics.
  • Appreciate and explore the role of Analog and Digital ICs in electronic components.
Semiconductor devices Semiconductor devices Electronic industries manufacture diodes, transistors, integrated circuits (ICs), etc, to develop different products for different applications. All these electronic devices are manufactured using semiconductor materials.
Introduction

Electronics is the field of science and engineering which deals with semiconductor devices and their utilization. In today's world, electronics deals with diodes, transistors and their circuits. Microelectronics represents the Integrated Circuit (IC) technology, in which a circuit consists of millions of electronic components such as diodes, rectifiers, transistors, resistors and capacitors on a single piece of semiconductor chip, of area 100 mm2.

The present age is called the age of electronics as electronics have a wide range of applications such as amplification, rectification, communication, industrial automation, control of power generation, biomedical equipments, calculators, microprocessors, mobiles, computers, consumer electronics and photo-electricity, etc. Presently, electronic industries manufacture diodes, transistors, operational amplifiers (OPAMPs), integrated circuits (ICs) etc., to develop different products for different applications. All electronics devices starting from individual discrete devices such as diodes to very large scale integrated circuits are manufactured using semiconductors materials.

Energy level of a chlorine atom Chlorine has 17 electrons and thus a configuration of 1s2 2s2 2p6 3s2 3p5. In this case the Energy Level 1 (K) contains 2 electrons (1s2 level), Energy Level 2 (L) contains 8 electrons (2s2 and 2p6 levels) and Energy Level 3 (M) contains only 7 electrons (3s2 and 3p5 levels). Though level 3 can hold 18 electrons, chlorine has only 7 electrons to be filled in level 3. Hence for chlorine, level 3 is the valence shell with 7 valence electrons.
Energy levels in an atom

Let us consider an isolated atom. We know that electrons revolve around the nucleus in fixed orbits in an atom. However, the electrons cannot choose any orbit they wish. They are restricted to orbits with only certain energies. The orbits are denoted by principal quantum numbers or K, L, M, N shells. Each orbit represents an energy level. Electrons are arranged in order of 2n2, where 'n' is the orbit or shell number. For example, first shell can accommodate 2 electrons, second 8, third 18, and so on. Electrons can jump from one energy level to another, but they can never have orbits with energies other than the allowed energy levels.

An electron orbiting very close to the nucleus in the first shell is very tightly bound to the nucleus and possesses only a small amount of energy. Hence first shell has lowest energy level. Greater the distance of an electron from the nucleus, the greater is its energy. Hence the energy level of the outermost shell is highest. Due to such high energy, the valence electrons in the outermost shell can be easily extracted. Such electrons take part in chemical reactions and in bonding the atoms together.

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