MSE Test Solving Strategies: Electronic Properties

Test Review Overview

• Summary of Electronic Properties Concepts

• Multiple Choice Test Example Concept Problems

• Calculation Test Example Problems

• Band Structure Schematic Test Example Problems

Electronic Properties Summary

Material Conductivity Increases with:(or Resistivity Decreases with)

Reasons:

Metals • Decreasing Temperature• Increasing Grain Size• Less Cold Work• Lower Level of Impurities

• Atom vibrations scatter e’s• Electrons scattered by defects

(impurities, dislocations, and grain boundaries)

Semiconductors • Increasing Temperature• Increasing Grain Size• Adding Impurity atoms

(Doping)

• Thermal energy creates e-h pairs

• Grain boundaries scatter e’s• Impurity atoms donate

electrons or electron holes

Insulators • Increasing Temperature • Thermal energy creates e-h pairs

Note: RESISTIVITY is the inverse of CONDUCTIVITY

Band Structures SummaryMetals

Band Structures (Cont.)

Semiconductors Insulators

Doped Semiconductorsp-Type Semiconductor Intrinsic Semiconductor n-Type Semiconductor

Group IV with Group III Impurity Atoms

Group IV withNo impurities

Group IV with Group V Impurity Atoms

More holes than electrons (Majority carriers are electron holes)

# electrons = # electron holes(electron-hole pairs)

More electrons than holes (Majority carriers are electrons)

Concept Question: Example 1

Which of the following terms refer to a Group IV n-type semiconductor?

A) donor

B) exhaustion

C) electron hole majority carrier

D) greater conductivity than p-type with same doping level

E) group III element impurities

Concept Question: Example 2

In comparison with intrinsic Si, a B doped Si wafer ( 1025As/m3) has ****

A) greater conductivity

B) a larger energy gap

C) has more n-type carriers

D) has more p-type carriers

E) equal number of p-type and n-type carriers

Concept Question: Example 3

Which of the following terms refer to semiconductor devices ****

A) bipolar pnp avalanche diode

B) solar cell

C) rectifier MOSFET

D) dual avalanche diode

E) light emitting diode

Concept Question: Example 4

Which of the following will increase the electrical conductivity for Pb?

A) Increasing temperature

B) Decreasing temperature

C) Adding a few % of Cu

D) Increasing the grain size

E) Deforming the metal by cold rolling it

Concept Question: Example 5

If the temperature in the room increases from 20C to 50C, conductivity will:

A) increase in a metal like Mg

B) increase in a doped semiconductor like n-type Si

C) increase in an intrinsic semiconductor like Ge

D) decrease in a metal like Cu

E) decrease in a semiconductor like Si

Calculations: Example 6

If an intrinsic semiconductor, Eg=.67ev has conductivity of 100 ohm-1 m-1 at 100C, what is the intrinsic carrier concentration if the mobilities are µe = 0.40 m2 / V-sec and µh = 0.20 m2 / V-sec.

Calculations: Example 7

What is the conductivity of a semiconductor if p-type dopant is added to achieve a concentration of 3.13 x 1021 atoms / m3? ( µe = 0.40 m2 / V-sec, µh = 0.20 m2 / V-sec )

Calculations: Example 8

How many grams of boron are required to achieve a concentration of 3.13 x 1021 atoms / m3 when added to 1 m3 a semiconductor material?

Band Structures: Example 9Draw the band structure for a metal like K (valence = K+1 when ionized), and a semiconductor like Si and briefly explain the reason for differences in conductivity for each type of material.

Band Structures: Example 10Using the band gap diagram schematics shown below, show and draw the charge carriers for intrinsic Si and B doped Si semiconductors.

Test Review Wrap-Up

• Summary of Electronic Properties Concepts

• Multiple Choice Test Example Concept Problems

• Calculation Test Example Problems

• Band Structure Schematic Test Example Problems