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Matlab电子电路分析(第三卷) 7 f1 q# T7 B* ]2 f2 d/ d& y, B' d8 K
CHAPTER TEN : n2 X# z# F3 v' @6 M
SEMICONDUCTOR PHYSICS
: {2 P) I" L# \4 K2 sIn this chapter, a brief description of the basic concepts governing the flow of [size=9.96001pt]current in a pn junction are discussed. Both intrinsic and extrinsic semicon6 X" `0 } k8 \& N5 F6 O' @0 h
ductors are discussed. The characteristics of depletion and diffusion capaci[size=9.96001pt]tance are explored through the use of example problems solved with
/ c2 ^7 y2 K0 G! d2 cMATLAB. The effect of doping concentration on the breakdown voltage of[size=9.96001pt]pn junctions is examined.3 m1 Q- N' p* V+ J2 |
10.1 INTRINSIC SEMICONDUCTORS ( |$ R! n( M% |7 g6 k
10.1.1 Energy bands
- ]) Q" y9 V4 IAccording to the planetary model of an isolated atom, the nucleus that con[size=9.96001pt]tains protons and neutrons constitutes most of the mass of the atom. Electrons
8 U( c/ J2 T% v# D# L. Esurround the nucleus in specific orbits. The electrons are negatively charged[size=9.96001pt]and the nucleus is positively charged. If an electron absorbs energy (in the+ c8 X; @& Z, ~! s
form of a photon), it moves to orbits further from the nucleus. An electron[size=9.96001pt]transition from a higher energy orbit to a lower energy orbit emits a photon for
/ I8 ^: ]7 J) ]# F5 ya direct band gap semiconductor. ! I) R" Y3 e& u! h% b9 D
The energy levels of the outer electrons form energy bands. In insulators, the[size=9.96001pt]lower energy band (valence band) is completely filled and the next energy
' a$ \( _% V* f& Uband (conduction band) is completely empty. The valence and conduction[size=9.96001pt]bands are separated by a forbidden energy gap.
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[size=9.96001pt]
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