EE 121b - 2 - Semiconductor Physics Review

EE 121b - 2 - Semiconductor Physics Review - Slide 2-1 EE...

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Unformatted text preview: Slide 2-1 EE 121B Chi On Chui EE 121B Principles of Semiconductor Device Design Semiconductor Physics Review Professor Chi On Chui Electrical Engineering Department University of California, Los Angeles Email: chui@ee.ucla.edu Slide 2-2 EE 121B Chi On Chui Outline Energy Bands and Charge Carriers in Semiconductors (Ch. 3) Carrier Transports by Drift and Diffusion Processes (Ch. 3 and 4) Slide 2-3 EE 121B Chi On Chui Electronic Structure and Energy Levels in a Si Atom 4 valence* electrons ( 3 s 2 3 p 2 ) * Valence is a measure of the number of chemical bonds formed by the atoms of a given element Energy levels in the coulombic potential of the nucleus Slide 2-4 EE 121B Chi On Chui 6N States 2N Electrons 2N States 2N Electrons 2N States 2N Electrons 8N States 4N Electrons 6N States 2N Electrons 4N States Electrons 4N States 4N Electrons Band gap E g Relative spacing of atoms Relative energy of electrons Energy Levels in Si with Smaller Interatomic Spacing N Slide 2-5 EE 121B Chi On Chui Insulators versus Semiconductors versus Metals Empty (unoccupied) states must be available to the electrons to move Semiconductors have much smaller E g than insulators such that many electrons can be thermally excited from the VB to the CB at RT (forming electron-hole pairs, EHPs) E g E g Insulator Semiconductor Metal Typical band structures at 0K Conduction Band (CB) Valence Band (VB) Semiconductor at room temperature E g E c E v an empty state in the VB is referred to as a hole EHP intrinsic carrier conc....
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EE 121b - 2 - Semiconductor Physics Review - Slide 2-1 EE...

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