MSE 250 Final exam

The band structure helps us to explain why impurities make the conductivity go __ for metals and __ for semiconductors.

a. down; up

The conductivity in doped semiconductors is affected by __ and __.

b. impurities; temperature

The temperature affects the __ of intrinsic semiconductors.

c. conductivity

Doped semiconductors can be __ or __.

b. p-type; n-type

Doped semiconductors are used to make __.

c. electronic devices

Elemental semiconductors are typically group __ materials.

d. IVA

Examples of elemental semiconductors are __ and __.

e. Si; Ge

Compound semiconductors include __ compounds and __ compounds.

a. III-V; II-VI

Examples of III-V compound semiconductors include __ and __.

b. GaAs; InSb

Examples of II-VI compound semiconductors include __ and __.

c. CdS; ZnTe

In compound semiconductors, the wider the __ difference between the constituting elements, the __ the energy bandgap.

b. electronegativity; wider

In an intrinsic semiconductor, the valence band is typically __ and the conduction band is typically __.

d. completely filled; completely empty

In an intrinsic conductor, __ causes the electron to jump from the __ band to the __ band.

b. thermal excitation; valence; conduction

In an intrinsic conductor, thermal excitation creates a free electron in the __ band and a corresponding __ in the __ band.

c. conduction; hole; valence

Conductivity is caused primarily by __ excitation in intrinsic semiconductors.

b. thermal

In a semiconductor, electrical conduction occurs by migration of __ and __ under the influence of an electric field.

c. electrons; holes

Electrical conductivity (in a semiconductors) can be calculated by the expression sigma = __ + __, where n is the number of electrons/m^3, p is the number of holes/m^3, e is the electron charge, mue is the electron mobility and muh is the hole mobility.

b. nemue; pemuh

The conductivity of pure silicon __ with increasing temperature.

c. increases

The conductivity of intrinsic semiconductors __ with increasing temperature.

c. increases

The conductivity of metals __ with increasing temperature.

a. decreases

The number of conduction electron in an intrinsic semiconductor is __ to __, where Egap is the energy bandgap, k is the Boltzmann constant, and T is the temperature of the semiconductor.

b. proportional; e^(-Egap/kT)

The bandgap of Si is __ eV.

c. 1.11

The bandgap of Ge is __ eV.

b. 0.67

The bandgap of CdS is __ eV.

d. 2.40

For the intrinsic semiconductor, the number of electrons is __ the number of holes.

b. equal to

In an extrinsic semiconductor, __ create __ electrons or holes.

c. impurities; excess

In an extrinsic semiconductor, the number of electrons is __ the number of holes.

b. is not equal to

When we dope group V atoms into a group IV matrix, we obtain a __ semiconductor.

a. n-type extrinsic

For an n-type semiconductor, the number of electrons is __ the number of holes.

d. much greater than

If you dope group IV silicon with group V phosphorus, the phosphorus atoms donate excess __ to the semiconductor.

b. electrons

When we dope group III atoms into a group IV matrix, we obtain a __ semiconductor

b. p-type extrinsic

For a p-type semiconductor, the number of electrons is __ the number of holes.

c. much lower than

If you dope group IV silicon with group III boron, the boron atoms donate excess __ to the semiconductor

a. holes

In an n-type semiconductor, the majority carriers are __.

b. electrons

In an n-type semiconductor, the minority carriers are __.

a. holes

Group V impurities have __ valence elctrons.

e. 5

When a group-V impurity is added to Si (a group IV matrix), __ valence electrons from impurity form __ bonds with the nearest Si atom __ electrons.

b. 4; covalent; valence

When a group-V impurity is added to Si (a group-IV matrix), the __ valence electron from the impurity is donated to the __ band if kT > __ MeV.

c. fifth; conduction; 44

Phosphorus substitutional atoms in a silicon are __ ionized at room temperature

c. fully

Donor exhaustion occurs in a n-type semiconductor when __ n-type dopant atoms in the material, have __ their extra electrons to the __ band.

d. all of the; donated; conduction

.Boron is a ___ dopant in Si and Ge semiconductors.

b. p-type

Aluminum is a __ dopant in Si and Ge semiconductors.

b. p-type

Phosphorus is a __ dopant in Si and Ge semiconductors.

a. n-type

Arsenic is a ___ dopant in Si and Ge semiconductors.

a. n-type

A group IV p-type semiconductor is semiconductor with intentionally added group __ impurities.

b. III

A p-type semiconductor is __ rich.

c. hole

A group III impurity has __ valence electrons.

b. 3

When a group-III impurity is added to Si (a group-IV matrix), ___ valence electrons from the impurity form ___ bonds with the nearest Si atom ___ electrons.

b. 3; covalent; valence

When a group-III impurity is added to Si (a group-IV matrix), the __ valence electron from the matrix silicon is donated to the __ band of the impurity atom, if kT > __ MeV.

c. fourth; valence; 45

Boron substitutional atoms in a silicon are __ ionized at room temperature.

c. fully

Acceptor saturation occurs in a p-type semiconductor when __ p-type dopant atoms have __ an electron from the __ band to create holes.

d. all of the; donated; conduction

In a p-type semiconductor, the majority carriers are __.

c. holes

In a p-type semiconductor the minority carriers are __.

b. electrons

For doped silicon, the conductivity ___ with increasing doping concentration

c. increases

For n-typed doped silicon, the activation energy is low enough for n-type atoms to donate __ to give the silicon __ band __.

c. electrons; conduction; electrons

For p-type doped silicon, the activation energy is low enough for p-type atoms to accept __ to give the silicon __ band __.

c. electrons; valence; holes

An extrinsic light doping level is __ /m^3 for phosphorus.

d. 1E21

At T < __ K, the thermal energy is too __ to excite donor electrons. This is called __.

c. 150; low; freeze-out

In an extrinsic semiconductor, conduction is extrinsic for temperatures between __ and __.

….

In an extrinsic semiconductor, conduction is __ for temperatures much greater than __.

c. intrinsic; 400K

The structure of glassy silicate ceramics can be modified by __ modifiers.

a. network

The properties of glassy silicate ceramics can be modified by modifying the __ of the materials.

b. structure

Flaws can significantly affect the __ of ceramics.

c. strength

There are different methods for making ceramics __.

b. strong

Ceramic materials can be classified as __, __, __, __, __ and __.

c. glasses; clays; refractories; abrasives; cements; advanced ceramics

Ceramic glasses can be used for __ applications.

b. optical and glass container

Ceramic clays can be used for __.

c. whiteware containers

Ceramic refractories can be used for __ for __ applications.

d. bricks; high temperature

Ceramic abrasives are used for __, __, and __ applications.

c. sandpaper; cutting; polishing

Ceramic cements are used for __ applications.

d. structural

Advanced ceramics are used for __ and __.

b. engine parts; sensors

Ceramic silicate glasses are __ silicates (SiO2) containing other __ such as __, __, __ and __.

d. non-crystalline; oxides; CaO; NaO2; K2O; Al2O3

Container/window glasses contain about __ wt% __ and __ oxides, whose __ are incorporated within the __ network.

a. 30; Ca; Na; Cations; SiO4

In soda-lime-silica flat glass, __ and __ are added into the glass to act as __ modifiers.

c. Ca; Na; network

In a sodium silicate glass, __ is the glass forming ion, __ is the modifying ion, and the oxygen can be __ and atoms.

b. silicon; sodium; bridging; nonbridging

The major types of glasses are __, __, __ and __ glasses.

e. soda lime; lead; borosilicate; high silica

Soda lime glass contains about 11% __ and about 13% __.

b. CaO; Na2O

Soda-lime glass is __ and __ to melt and shape.

a. inexpensive; easy

The most widely used glass is __ glass.

b. soda-lime

Soda-lime glass is used for __, __, __, and __.

c. windows; bottles; light bulbs; jars

Soda-lime glass has __ durability, __ chemically resistant, and has __ thermal-shock resistance.

c. poor; is not; poor

Lead glass contains 20-30% lead __.

c. oxide

Lead glass has __ density, is __, and is very __ to melt and shape, cut and engrave.

d. high; brilliant; easy

Lead glass has __ durability and is __ to scratch.

b. poor; easy

Lead glass is used for __, __ and __.

a. fine crystal; radiation windows; TV tube parts

Borosilicate glass usually contains 5-13% of boron __.

b. oxide

Borosilicate glass has very __ thermal shock resistance, very __ chemical durability; it is __ to melt and shape.

a. good; good; easy

Borosilicate glass is not suitable for __ applications.

b. long-term high temperature

Borosilicate glass is used for __, __, __ and __.

b. labware; kitchenware; glass pipe; sealed-beam headlights

High silica glass is typically 96-100% silicon __.

b. oxide

Fused quartz glass is __% silica.

b. 100

High-silica glass has __ thermal resistance.

c. outstanding

High-silica glass is __ to make and very __.

a. difficult; expensive

High-silica glass is used for __, __ and __.

d. spacecraft windows; labware; fiber optics

Borosilicate glass is also called __ glass.

b. Pyrex

Soda-lime glass is also called __ glass.

a. container

Fiberglass contains __, __, __ and __ oxides.

c. Ca; Al; B; Mg

Fiberglass is __ to draw into fibers, and it is used in glass- __ composites.

d. easy; resin

The viscosity of a glass typically __ as the temperature is increased.

b. decreases

The units of viscosity are __ or __.

d. Pascal-seconds; Poise