Lecture 5 - Carrier Distributions and Concentrations

Lecture 5 - Carrier Distributions and Concentrations -...

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1 EE360 – Lecture 5 Carrier Distributions and Concentrations Objective : 1. Understand the electronic properties of semiconductor materials. Questions to be answered : – How do we determine the energy distribution and concentration of carriers? – What do we mean by the “Fermi level?” – How do we quickly determine the concentration of carriers in most practical cases? EE360 – Lecture 5 Carrier Distribution: Preview • Goal: To determine the number of carriers per unit volume per unit energy as a function of energy: (number of carriers/cm 3 /eV) for a particular semiconductor • Approach: – Determine the number of energy states per unit volume per unit energy (states/cm 3 /eV) – Determine the probability of an electron occupying a state at a given energy – Multiply the two expressions carriers/cm 3 /eV E Example Carrier Distribution From Pierret, p. 38

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2 EE360 – Lecture 5 Density of States • Density of states: the number of allowed energy states per unit volume per unit energy • Units: states/cm 3 /eV g C ( E ) = conduction band density of states g V ( E ) = valence band density of states • Football Stadium Analogy: The number of seats at a certain distance from the field number of states with a certain energy From www.ukathletics.com EE360 – Lecture 5 Density of States (continued) • To actually calculate density of states we need quantum mechanics, but here are the results: Units: states/cm
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This note was uploaded on 04/20/2008 for the course EE 360 taught by Professor Hastings during the Spring '08 term at Kentucky.

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Lecture 5 - Carrier Distributions and Concentrations -...

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