Semiconductors

A Conductor is

a material through which electricity passes easily because it has free electrons

What material offers very little resistances to the flow of electrons?

Conductors

What 3 metals/conductors allow electricity to pass easily?

Silver copper and aluminum

Silver is a better conductor than ?

copper

Copper is used more frequently because ?

Because it is cheaper

Aluminum is used as?

Is used as a conductor where light weight is important

Why are some materials good conductors ?

One of the most important reasons is the presence of free electrons.

If a material has many electrons that are free to move away from their atoms , that material will be ?

That material will be a good conductor of electricity

Although free electrons usually move in a haphazard (lacking any obvious principle of organization) way , their movement can be ?

There movement can be controlled (electric current )

Electric current is a flow that control ?

electrons to move in the same direction

Conductors may be in the from of?

Bars , tubes, or sheets

The most familiar conductors are ?

Wire

To prevent conductors from touching at the wrong places they are usually coated with plastic, rubber , or cloth material called and ?

Insulator or insulation

various electrical applications require different ?

Different conductor sizes

Electrical wire -

is designed by definite gauge sizes that designate wire of a specific diameter.

As the diameter of wire decrease , The gauge number increase this is an example of

Inversely proportional

Copper wire is often stranded because stranded wire is ?

Stranded wire is easily bent without breaking

To bend or flex wire constantly , it is necessary to ?

To make many smaller strands into a cable or bundle. This allows for the flexing of the cable or wire without breaking

What is lamp cord made of ?

The lamp cord in your home is made of fine strands of copper wire. This allows it to be flexible and bend where you want it on the way from the plug to the lamp.

Larger wire used for wiring commercial or industrial buildings are ?

Are also stranded

Any number of small wire are grouped In a cable to carry ?

To carry the same amount of current a solid conductor wire

The larger wires have to be stranded because ?

Larger wires have to be stranded so they'll be easier to bend and work with if not it would be impossible to work with them

A solid No. 18 wire

is easily bent , but it's not as flexible as a multiple-strand cable

multiple-strand cable -

made up of smaller gage wire to equal the No.18 wire used in lamp

Insulator

a material with very few , if any, free electrons

No known material is a perfect insulator , however there at materials that are poor conductors that are classified as insulators such as,

Glass , dry wood , rubber, mica , and certain plastics

in between insulators and conductors are?

Semiconductors

semiconductors are

Materials that have conductivity properties about halfway between good conductors and good resistors

semiconductor materials are
the foundation of the vast array of electronic devices that surround us including

Computers, telephones, radios , televisions , refrigerators , microwave ovens , automobiles , airplanes, traffic lights , light-emitting diodes (LEDs)

Diode

a semiconductor device with terminals , typically allowing the flow of current in one direction only

The properties of semiconductor materials are

Silicon and germanium

Silicon and germanium are useful in electronic devices like

Integrated circuits , chips, transistors , diodes, & solar cells.

Semiconductor solar photovoltaic panels directly covert light energy into

Electrical energy

The electronic properties and conductivity of a pure or intrinsic semiconductor material can be changed in a controlled way to make them limited and predictable conductors by adding very small quantities of other elements such as

Boron or phosphorous to the melted semiconductor and then letting them melt to solidify back into a crystal form .

semiconductor is applied to both

Diodes and transistors as well as certain special types of electronic devices

germanium and silicon perform somewhere between the level of

Conductor and insulator in terms of opposition to current flow

The amount of opposition is programmed into it manufactured into the device by

Controlling the impurities introduced into pure germanium or pure silicon

Germanium and silicon can be purified to better than

99.999999 percent

By controlling the amount of doping agent introduced into each crystalline structure, manufactures can control

Can control the amount of opposition to current flow

Semiconductor diode is made by

Joining a piece of P material with a piece of N material

The place where two materials are joined is referred to as

the junction

The Junction is

Very thin , and each end had a piece if wire attached for connecting the diode , thus making a circuit

Both holes and electrons are involved in

Conduction in the PN junction diode

The holes in the N material near the junction are attracted by

Attracted by the negative ions on the P side of the junction and pass across the junction

Free electrons produced on the P side of the junction pass across the junction and

And neutralize positive ions on the N side ( example of intrinsic conduction)

Because of intrinsic conduction the junction is no longer

Is no longer a rectifier when an external voltage is applied across it

The point contact diode

is a very small unit that is used for rectifying signals.

Rectifying power

line frequencies and higher currents.

Unlike the junction diode , the point contact type depends on

Depends on the pressure or contact between a point and a semiconductor crystal for its operation

In a point contact diode

one section consists of a small , rectangular crystal of N material (either germanium or silicon) and a fine beryllium copper, phosphor-bronze , or tungsten wire called the cat whisker

Cat whiskers

presses against the semiconductor material and forms the other part of the diode

The reason for using a fine - pointed wire instead of a flag metal plate is to produce

Produce a high density electric file by the point of contact without using too large external voltage source.

The opposite end of the cat whiskers is used as

The diode terminal for connection purposes

Since the size of the cat whisker is limited , the amount of current the diode can handle is also limited

Tunnel Diodes

Tunnel diodes can be used in extremely small spaces , such as

part of an integrated circuit (IC) or chip.

Tunnel diodes can switch at

very high rates [ 2 to 10 gigahertz (GHz) ]

A gigahertz

is 1,000 megahertz (MHz)/ 1 billion times per second

Tunnel diodes are doped by using

Gallium arsenide, gallium antimonide, and indium antimonide

A megahertz is

1 million times per second

Silicon - controlled rectifier (SCR)

is a specialized rectifier or diode; is a specialized four-layer type of device used for the control of current on its cathode-to-anode path.

What is used to control the resistance between the cathode and anode?

a gate

An SCR conducts current in

In the forward direction only

Examples of SCR are

Light dimmer and the speed control for an electrically powered small hand drill

what is a feature of a conductor regarding their atomic structreq

less than 4 electrons in its valence band

this overlaps with the conduction band

what is a insulator

a material with no free electrons

What is a diffrence between conductors and a semi conductor

a semi conductors valence shell does not overlap with conductors

what is doping

adding very small amounts of a different element with either more, or less electrons in its outer shell.

what is the process of doping

an impurity is introduced into the semi conductor in order to change its electrical conductivity

it allows it to act like either a semi conductor or in insulator

N type conductor what is it.

add a small number of atoms aresenic (As) with five outer electrons in its outer shell to pure silicon with four. we end up with a spare electron in the conductor layer.

because atom can have 8 in this band because its silicon and we bond them we would have an extra electron this process is what doping is

we do this because that free electron can now carry charge make it N(egative) type

What is a P type semi conductor

now beacause silicon has four outer electrons if we add something like gallium with 3 outer electrons gives 7 not 8 outer electrons leaving a hole that can attract electrons

this creates electric current

P(ostive) type

what happens if we attach a piece of P type to a piece of N type

we get a “depletion layer” because its depleted of free charge carriers

what is a diode and its property

n type joined to p type doped semi conductor

its fundamental property is to conduct electric current in only one direction

how can we use the diode and how does it work

force current in one direction by reinforcing/eliminating the depletion layer can flow across the diode

what is a transistor

two diodes using three layers of semi conductor

what if we apply two different power supplies with enough voltafe to a two diodes

becomes transistor which functions as an electron switch

how can we use semi conductors to create a switch

we need three layers of them

what is a photodiode

a semi conductor that converts light into electrical current

the current is generated when photons are absorbed by the photodiode

the light energy creates a hole within the depletion layer which allows current to flow

at night what does the photodiode do

its semiconductor acts as an insulator and at day its a conductor

what is CCDs

2d rays of photodioded that chanhe light into a grid of electrical charge

all of the photodiode is a pixel. so more light on it means more charge created

what must we do to the charge in photodiode to make it useful

moved to main memory using a shift byte by byte

Semiconductor

Materials that conduct electricity at values between that of a pure metal and a good insulator.

Doping

The process of adding impurities to pure semiconductors to enhance their conductivity.

N-Type

Materials with negatively-charged carriers (free electrons) due to the presence of donor impurities, determining conductivity.

P-Type

Materials with positively-charged carriers ("holes") due to the presence of acceptor impurities, determining conductivity.

P-N junction diode

Formed by joining a P-Type semiconductor to an N-Type semiconductor, creating a single semiconductor-crystal structure.

Magnet

Any material or object that produces a magnetic field.

Magnetic Field

A volume of space where magnetic forces are exerted.

Law of Magnetism

Like poles repel, unlike poles attract.

Magnetization

The process where a magnetic material acquires magnetism, either temporarily or permanently.

Electromagnet

A current-carrying conductor wrapped around an iron core.

Magnetic Flux

The number of lines of force in a magnetic field (φ).

Magnetic Flux Density

The number of lines of force per unit area in a given magnetic field (B).

Neutral Point

The point between magnetic fields where magnetic flux density is 0.

Angle of DIP

The angle between Earth's magnetic flux and the horizontal.

Angle of DECLINATION

The angle between magnetic North and geographic North.

What is the relationship between temperature and carrier concentration in intrinsic semiconductors?

Carrier concentration increases with temperature due to more electron-hole pairs being generated.

What are majority and minority carriers in semiconductors?

Majority carriers are the most abundant type of charge carrier in a doped semiconductor (electrons in n-type, holes in p-type), while minority carriers are the least abundant.

Define the term "acceptor" in the context of semiconductors.

An acceptor is an impurity atom that increases the number of holes (p-type).

What happens to the conductivity of an intrinsic semiconductor as temperature increases?

The conductivity increases rapidly due to the generation of more electron-hole pairs.