p-type Semiconductor

Chapter 9.7 p-type Semiconductor

Fundamental Electrical and Electronic Principles Third Edition Book
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Fundamental Electrical and Electronic Principles Third Edition Book

  • 270Fundamental Electrical and Electronic Principles The circuit action when a battery is connected across the material is illustrated in Fig. 9.6 . Once more, only electrons fl ow around the external circuit, whilst within the semiconductor there will be movement of majority carriers in one direction and minority carriers in the opposite direction. 9.7 p-type Semiconductor In this case a trivalent impurity such as aluminium (Al), gallium (Ga), or indium (In) is introduced. These impurity atoms also join the covalent bonding system, but since they have only three valence electrons there will be a gap or hole in the bond where an electron would normally be required. Due to electron-hole pair generation in the lattice, this hole will soon become fi lled, and hence the hole will have effectively drifted off elsewhere in the lattice. Since each impurity atom will have accepted an extra electron into its valence band they are known as acceptor impurities, and become fi xed negative ions. The result of the doping process is illustrated in Fig. 9.7 . SiSiSiSiSiSiSiAle–hpair Fig. 9.7 holeselectronsI Fig. 9.6