Chapter 3 Lecture - Part 5

Vs plot is for lightly doped n type si three regions

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Unformatted text preview: p --> high 1/T, etc. vs – Plot is for lightly doped, n-type Si • Three regions of interest – At low temps, donors haven’t yielded all their available At electrons, so donor atoms are in the “ionization” stage, hence Si is in the ionization region. Also EHP generation is not that large. is Figure 3—18 Carrier concentration vs. inverse temperature for Si doped with 1015 donors/cm3. Carrier Concentrations Carrier Electron and Hole Concentrations and Equilibrium – At moderate temperatures • dopant is fully ionized - no more electrons to donate • EHP generation increases as T increases, but is insignificant EHP relative to number of electrons from donor. relative • Called extrinsic region • n0 insensitive to big changes in T. Excellent for device operation. operation. – At high temperatures • no additional electrons from donors • EHP generation is now significant and begins dominating n 0. • Si looks “intrinsic” since EHP generation is the dominant Si means to create conduction electrons. means Carrier Concentrations Carrier Compensation • Real semiconductors contain both donors and Real acceptor impurities to some degree. This can modify conduction if the number of unwanted impurity atoms is significant. atoms • Fig. 3-19 shows energy bands for compensation in Fig. an n-type conductor. an – Ea is full of electrons because EF >>>...
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