Lecture 5 - Density of States and Intrinsic Carrier Density

# Lecture 5 - Density of States and Intrinsic Carrier Density...

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1 Introduction to Semiconductor Devices Instructor : Ridha Kamoua Stony Brook University Lecture Notes Density of States and Intrinsic Carrier Density

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2 Learning Outcomes: 1. Describe concept of energy density of states 2. Describe the Fermi-Dirac Distribution 3. Describe Maxwell-Boltzmann approximation 4. Determine thermal equilibrium carrier density in an intrinsic semiconductor
Effective Mass A free electron has a mass m 0 and obeys Newton’s equation: In a crystal, the electron sees an additional internal force due to background potential of the lattice atoms. We want to include the effect of internal forces in the mass expression such that: 0 m F ext 0 int m F F , m F m * is the effective mass 22 * From E 2 k m acceleration

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Structure and occupation of energy bands in a crystal determine if a material is a metal, insulator, or semiconductor. A completely filled or empty band cannot carry current. A semiconductor can be considered as an insulator with a small energy bandgap. At 0K, the semiconductor is an insulator. Semiconductor conductivity can be controlled by: temperature, doping, light,… Metals have partially filled bands which leads to high conductivity. Si Ge GaAs diamond SiO 2 E g (eV) 1.12 0.66 1.42 5 8 Metals, Insulators, Semiconductors
Metals, Insulators, Semiconductors Insulators Semiconductors Metals Low conductivity Controllable conductivity High conductivity

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6 Consider a metal as a 3-D infinite potential well. Define the
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## This note was uploaded on 10/03/2010 for the course ESE 231 taught by Professor Kamoua,r during the Spring '08 term at SUNY Stony Brook.

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Lecture 5 - Density of States and Intrinsic Carrier Density...

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