Electronic Devices Lectures

how does f(E) depend on temperature?

it gradually increases as temperature increases.

what is the occupancy of a state at E = Ef?

50%

what is the fermi energy of fermi level Ef?

the eneryg where seeing an electron is 50%

how does density of states g(E) depend on energy E?

Regardless of E, g(E) stays the same. no dependancy

which groups form semiconductors?

II, III, IV, V, VI. ie (1-6_

miller index direction syntax

[]

miller index surface syntax

()

wafer thickness or chip size

mils (10e-3 inches = 25.4 micrometers)

ni of silicon

1×10^10 / cm³

crystalline silicon band electrons

not tied to or associated with any one particular atom

forbidden zone

a crystal containing only Si atoms with no impurities gives rise to the conduction and valence bands with no levels in the band gap

what are the n values for shell k, shell L, shell m, shell n,

1 , 2, 3, 4

Ideal Component

A component that takes no space, weighs nothing, uses no power, costs nothing, requires no maintenance, no training to operate, and lasts forever.

“Smart weightless power costs more training but lasts forever.”

Conductivity Equation

Describes the relationship between resistance, current, electron charge, number of free electrons, and holes in a semiconductor.

o   Q = 1.602 * 10^-19  (c) =  Electron charge

o   N – number of free electrons (e-)

o   P – number of free holes (h+)

o   Mn -  how fast the e- is moving

o   Mp – how fast the h+ is moving

Semiconductor Types

Classification into elemental and compound semiconductors, focusing on Si, Ge, Ga, As, and their applications.

Crystal Growth

The process of making semiconductors, including crystal structure, wafer slicing, and different lattice types.

Energy Levels, Bonds, and Bands

Concepts related to electronic atom structure, energy bands, covalent bonds, and carriers in semiconductors.

Fermi Function f(E)

Gives the probability of a state being occupied by an electron, influencing the behavior of electrons in a semiconductor crystal.

Density of States g(E)

The number of available states for electrons in a semiconductor, crucial for understanding electron occupancy and behavior.

an si atom has how many electrons

14

how many atoms are there in the three dimensional diamond lattice unit cell?

8

Bell Labs (1947)

the 1^st transistor was made.

o   John Bardeen

o   Walter Brattain

o   William Shockley

device dimensions

o   Microns (micrometers) – 10^-6

·Oxide thickness

o   Angdstroms (A) or nanometers (nm) – 10^-9

wafer diameters

o   Millimeters(mm) or inches

conductivity is determined by the number of __ and __.

electrons and holes

resistivity is the inverse of _______

conductivity

Elemental

using one material

Compound

uses more than one material

semiconductor - group IV

silicon is the most common

in most integrated circuits and power devices

semiconductor- group III and V

GeAs is most common

light emitting - GaN, GaAsP

optical communication - GaLnAsp

semiconductor - group II and VI

lightning arresters - ZnO

Infrared detectors - HgCdTe

how to make a semiconductor

o   Bring single crystal seed into the melt

o   Dip seed into melt and withdraw slowly

o   Pull seed with proper pull rate and rotation

for slicing wafers, what is used?

a wire coated in diamond splinters

1 cpu = _____ mm²

506

Crystals structure - amorphous

§  Randomly distributed, working like an insulator (glass)

Crystals structure - Polycrystalline

Metal, some organization, working like an conductor (most metals)

Crystals structure - single crystal

very organized - semi-conductor - (silicone wafer)

simple cubic lattice

atoms on every corner totaling 1 atom

body centered cubic (bcc)

atoms on every corner AND 1 in the middle totaling 2 atoms

face centered (fcc)

atoms on every corner AND 1 atom on the surface of each face of the cube totaling 4 atoms.

diamond lattice

fcc with 4 additional atoms in the box totaling 8 atoms.

unit cell

small portion of any crystal that could be used to reproduce the crystal

doesnt have to be primitive, the smallest unit cell possible

miller indices

numbers that specify the wafer surfaces

find x, y and z

inverse them

normalize the lowest integers

zincblende structure

same as a diamond lattice EXCEPT there are two different types of atoms in the lattice

GaAs, InP, GaP,

miller indices cannot be established for a plane passing through the ____.

orgin

isolated atom

an atomic core or nucleus surrounded by electrons

principle quantum numbers (n)

determines the energy of an election

Azimuthal quantum number (l)

determines the angular momentum magnitude.

each value of l constitutes a subshell

conduction band (Ec)

higher band, can hold 8 electrons

band gap (Eg)

amount of energy gained or lost by the charge of a single electron moved across an electric potential different of 1 volt

electrons cannot exist in this gap

determines the characteristics of the device (ie. metal, semiconductor, insulator)

what is the band gap (Eg) of silicone?

1.12 eV

lower band gap energy = lower _________ = higher ______________

resistance, conductivity

at low temperatures, there are no electrons in the ____________ band and no holes in the ____________ band. aka..there is no current.

conduction, valence

free electrons

only in the conduction band

free holes

only in the valence band

current equation

i = dQ/Dt

Q = charge = free electrons and free holes

electron hole pair (EHP)

for every free hole there is a free electron

dopant atoms

specific impurities added to semiconductors

donor atom

group V atoms (P, As, Sb)

Extra electron

At higher temps, donor donates extra electron

n - type (electrons are majority carrier)

Acceptor atom

group III atoms (B, Ga, In)

missing an electron

at higher temps, acceptor takes an electron

P-type

intrinsic semiconductor

undoped semiconductor sample containing any significant amount of impurity atom

number of electrons (n) = number of holes(i) = ni

ni for si = 1×10^10 cm³

extrinsic semicondcutor

doped semiconductor

majority carrier

the most abundant carrier in a given semiconductor sample

electrons in an n-type material

minority carrier

the least abundant carrier in a given semiconductor sample

holes in an n-type material

density of states

number of chairs available for electrons

effective mass (Mn*)

mass of electrons in a crystal. different from the mass of electrons in the free space

fermi function f(E)

gives the probability of a state being occupied by an election

fermi energy Ef

where the probability of seeing an electron is 50%. going up decreased the probability but going down increases the probability

boltzmann constant (k)

8.617 × 10^(-5)

electron density

depends on the area under the (E - Ec) vs gc(e) curve

what material parameters determine the semiconductor resistivity?

carrier density (electron and hole) and mobility

which one material parameter influence the semiconductor resistivity the most?

dopant density

what shell do si atoms have 4 electrons in?

M shell

charge of electron

1.6 × 10^-19 C

how many atoms are there in the (100) plane?

2