Introduction of Semiconductor Physics

UNIT II

CHAPTER 2

SEMI CONDUCTOR PHYSICS

Introduction -Properties of Semiconductor-Direct and Indirect Band Gap Semiconductors -Types of Semiconductors -Intrinsic Semiconductor -Density of Electrons in Conduction Band - Density of Holes in Valence Band -Variation of Fermi Energy Level and Carrier Concentration With Temperature in an Intrinsic Semiconductor Mobility and Electrical Conductivity of Intrinsic Semiconductors Determination of Band Gap Energy -Extrinsic Semiconductor -Carrier Concentration in N-u Type Semiconductor -Carrier Concentration in P-type Semiconductor-Variation of Fermi Energy Level With -Temperature and Impurity Concentration in P-type Semiconductor -Variation of Carrier Concentration With Temperature -Carrier Transport in Semiconductor - Velocity -Electric Field Relations and Mobility of Charge Carriers -Drift and Diffusion Transport-Einstein Relation [for Reference Purpose] - Effect of Temperature on Carrier Transport -Hall Effect -Device To Find Hall Effect [Experiment] - Applications of Hall Effect -Ohmic Contact -Schottky Diode 

INTRODUCTION

We know materials are classified on the basis of conductivity and resistivity. Semiconductors are the materials which has conductivity, resistivity inbetween conductors and insulators. The resistivity of a semiconductor is in the order of 10^-4 to 0.5 ohm-metre.

It is not that resistivity alone decides whether a substance is a semiconductor (or) not, because some alloys have resistivity which are in the range of semiconductor's resistivity. Hence, there are some other properties like band gap which distinguishes the materials as conductors, semiconductors and insulators.

A semiconductor is a solid which has the energy band similar to that of an insulator. It acts as an insulator at absolute zero and as a conductor at high temperatures and in the presence of impurities.