Transcription of 1. Carrier Concentration
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1. Carrier Concentration
1. Carrier Concentration a) Intrinsic Semiconductors - Pure single-crystal material For an intrinsic semiconductor, the Concentration of electrons in the conduction band is equal to the Concentration of holes in the valence band. We may denote, ni : intrinsic electron Concentration pi : intrinsic hole Concentration However, ni = pi Simply, ni :intrinsic Carrier Concentration , which refers to either the intrinsic electron or hole Concentration Commonly accepted values of ni at T = 300 K Silicon x 1010 cm-3 gallium arsenide x 106 cm-3 Germanium x 1013 cm-3 b) Extrinsic Semiconductors - Doped material The doping process can greatly alter the electrical characteristics of the semiconductor. This doped semiconductor is called an extrinsic material. n-Type Semiconductors (negatively charged electron by adding donor) p-Type Semiconductors (positively charged hole by adding acceptor) c) Mass-Action Law n0 : thermal-equilibrium Concentration of electrons p0 : thermal-equilibrium Concentration of holes n0p0 = ni2 = f(T) (function of temperature) The product of n0 and po is always a constant for a given semiconductor material at a given temperature.
Gallium arsenide 1.8 x 106 cm-3 Germanium 2.4 x 1013 cm-3 b) Extrinsic Semiconductors - Doped material The doping process can greatly alter the electrical characteristics of the semiconductor. This doped semiconductor is called an extrinsic material. n-Type Semiconductors (negatively charged electron by adding donor)
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