8/13/2019 A MT Ch01 Introduction & Crystals
1/14
Chapter1page1
MicroelectronicsTechnology
E.F.Schubert2012,allrightsreserved
RensselaerPolytechnicInstituteTroy,NewYork
SolidStateDevices
Examplesare:o
Field
effect
transistors
o Bipolartransistorso LEDs
oLasers
o Photodetectorso Solarcells
8/13/2019 A MT Ch01 Introduction & Crystals
2/14
S
T
everalimpo
o Transo Geneo Reco
ransportof
o TransDiffu
>0K,
o Trans
moti
Trans
rtantphysic
portofchar
ationofch
binationo
electrons
port due t
ion isther
whenthese
Synonyms
motion;B
Diffusion
performe
DiffusionNetdiffusi
Netdiffusi
portdue t
nofcharge
The direc
particles
electricfi
Negative
Cha
portofcarralmechanis
gecarriers(
rgecarriers
charge
car
thermal e
ndommov
particlesh
for Diffus
ownianmo
or therm
byRobert
esultsin
ca
onoccursa
onoccursa
anelectri
particlesc
tion of car
nd is dire
ld
lectronsdri
pter1page2
ersbydiffumsdetermi
e.g.electro
iers
nergy of c
ementofp
veatherm
ion: Therm
tion
l motion
BrownB
riertransp
longtheco
longthepo
field D
ausedbyan
rier drift d
ted either
ftagainst
t
sionanddrnethebeha
s)
rriers
articles(e.g
alenergygr
al motion;
was first
rownianm
rtifthere
i
centration
itivexdire
rift.What i
electricfiel
epends on
along or a
edirection
iftviorofchar
iffusion. W
.electrons)
eaterthanz
Random
identified
tion
aconcentr
gradient
tion
sdrift?Dri
d.
the charge
gainst the
ofthe
elect
ecarriers:
hat is diffu
attempera
ero.
otion; Dif
in experi
ationgradie
t is thedir
polarity o
direction o
ricfield
sion?
tures
usive
ents
nt
cted
f the
f the
8/13/2019 A MT Ch01 Introduction & Crystals
3/14
R
a
a
I
hmslaw:
o V=Vo R=Ro I=Cu
ecall
nd
nd
sertionof
=urrent I
densurrent
o e=elo n=co v=avo =c
B
ltage
sistance
rrent
q.(2),(3),a
timunit
charge=
J =ty
mentaryc
ncentration
erageveloci
nductivity
Cha
asiclawof
nd(4)into
n
e
e
Area
numbe
arge=1.60
ofelectron
tyofelectr
pter1page3
ransport:IRV
A
lR
AJI
lV E
q.(1)yields
EJ
timeunit
elofumber
timenit
electronof
eJ
21019
C
spercm3
ns
hmslaw
A
l
1
ectrons
vne
s
vn
(1)
(2)
(3)
(4)
(5)
(6)
8/13/2019 A MT Ch01 Introduction & Crystals
4/14
erivationo
o Consi
o Neleo Conco Theao Curreo wh
:
derelectron
tronsarein
ntration=
eragevelo
ntdensity:
twastobe
Cha
sinavolu
sidethevol
xA
N
d
ityofcarrie
=
A
eJ
d
shown
pter1page4
eJ
eV=Adx
ume
rsis=
v
xA
Ne
t
d
vn
t
x
d
d
et
x
d
d
v
(7)
8/13/2019 A MT Ch01 Introduction & Crystals
5/14
R C
T H R
esistivity=
onductivity
heresistivit
owmanyo
easonfort
o Insulo Metao Semi
o What
o Exam
=
showsala
dersofma
elargevari
tor:
:
onductor:
isthereaso
Chemical
Differenc
Differe
ples:
Metal:
Semicond
Insulator:
Cha
Conducti
rgevariatio
nitude?
tion:Conc
Allelec
Electro
Some
nforthese
atureofel
sintheche
nceinnum
ctor:
pter1page5
ityandresidimension
dimension
ntrationof
tronsareti
nscanfreel
lectronsca
onductivit
mentorco
micalbond
eroffreee
n=1022
n=1015
n=105
stivity)= cm
)= 1
c
electrons:
htlybound
moveabo
freelymo
difference
mpound
lectrons
cm3
020
cm3
cm3
1=Scm
1
toatoms
utthemeta
eaboutthe
?
l
crystal
8/13/2019 A MT Ch01 Introduction & Crystals
6/14
C
E
E E
F
Eo
o
E
hemicalmo
amples:
lectroninv
lectronina
reeelectron
lectronsin
Collisions Electrons
lectrostatic
del:Electro
cuum =
solid =
s = fre
= fre
Fr
olids:
withlattice
feelelect
potentialin
Cha
Freeeleisnotlocal
trulyfree
quasifree
etomovea
etomovei
eelectrons
atomsare
rostaticpot
asolid:
pter1page6
ctronsinaizedinapa
lectron
electron
bout(diffus
anelectric
canforma
ossible
ntialofcry
olidrticularche
ion)
field(drift)
electrical
stallattice
icalbond
urrent
8/13/2019 A MT Ch01 Introduction & Crystals
7/14
Chapter1page7
o Collisionswithlatticeatomsareminimizedinastrictlyperiodicpotential,thatis,inacrystallinesolid
o Influenceofthelatticeistakenintoaccountbyaneffectivemassofelectrons Example: me = 9.11031kg (freeelectron) me* = 6.11032kg=0.067me (electroninGaAs)
Comparison:Crystallinesolidversusamorphoussolido Highpuritycrystallinesolid=hightechnologysolid
Example:Laser,LED,integratedcircuit,microprocessorchipo Amorphoussolid=lowcostsolid
Example:AmorphousSisolarcell
8/13/2019 A MT Ch01 Introduction & Crystals
8/14
T
T
herearedif
o Singlo Poly
o Whico Whico Whic
herearedif
o Simplo Bodyo Faceo Whato
What
erenttypes
crystalline
rystallines
onehasth
onehasth
oneiseasi
erentcryst
ecubiccrys
centeredcu
enteredcu
isthedefini
is
the
defini
Cha
ofsolids:
solids
lids
ehighestm
ehighestel
esttofabric
lstructure
al
biccrystal
iccrystal
tionofthe
tion
of
a
un
pter1page8
Crystals
echanicalst
ctricalcon
ate?
.Common
atticecons
it
cell?
o
rength?
uctivity?
rystalstruc
anta0?
morphous
turesare:
olids
8/13/2019 A MT Ch01 Introduction & Crystals
9/14
8/13/2019 A MT Ch01 Introduction & Crystals
10/14
o Vapo
o Other
pnjunctio
Heterostr
PhaseEpit
Whyisitc
Chemical Si:
GaGrowtha
growthtec
Cha
ngrowth(e
cturegrow
xy(VPE)is
alledVapor
eactionfor
As:
paratus:Se
nique:Mol
ter1page10
.g.pnjuncti
th(e.g.AlA
acommon
PhaseEpit
thegrowth
SiH4 Si
(CH3)3Ga+
eillustratio
ecularbea
onLED)
/GaAs)
pitaxialgro
xy?
of
+ 2H2
sH3 G
Epitaxy(
wthtechniq
As+3CH4
BE,notdisc
ue
ussedhere)
8/13/2019 A MT Ch01 Introduction & Crystals
11/14
8/13/2019 A MT Ch01 Introduction & Crystals
12/14
Chapter1page12
Thefourtypesofcrystals
Recallsomechemistryo Atomshaveelectronshellso Acompletelyfilledshellhas2,8,or18electronso Noblegaseshave2(He),10(Ne),18(Ar),,electronso Noblegasesareverystableanddonotreactwithotheratomso Atomshavethetendencytoassumeanoblegaselectronconfiguration
Thereare4mainclassesofcrystals:o Metalliccrystalso Ioniccrystals o Covalentcrystalso Molecularcrystalso Next,wewilldiscussthese4typesofcrystals
1. Metalliccrystals Consideranatomwithonelooselyboundelectron:
o Na (11electrons=2+8+1electron)o Cu (29electrons=2+8+18+1electron)
Inmetalliccrystals,electronsbecomepracticallyfree Thepositivelychargedioncoresareheldtogetherbyaseaofelectrons Metalliccrystalshavehighelectricalconductivity
Example:
Copper,
Cu
o 29protons,29electrons,34neutronso Molarmass=(29+34)g/mol=63g/molo Avogadrosnumber=61023atoms/molo MassdensityofCu=9g/cm3o Atoms per cm3 = 6 1023 atoms/mol (1/63) mol/g 9 g/cm3 =
=8.51022
atoms/cm3
o Electronspercm3=8.51022electrons/cm3
2. Ioniccrystals Twotypesofatomswithlargedifferenceinelectronegativity Oneatomhasalooselyboundelectron One atom has one electronmissing from a noblegas configuration (this is a highly
electronegativeatom) Transferofthelooselyboundelectrontotheelectronegativeatomoccurs
8/13/2019 A MT Ch01 Introduction & Crystals
13/14
T
I E
3. Cova
A B
E
hustheioni
ofreeelect
niccrystals
xample:So
o Nao Clo NaCli
lentcrystal
tomswithp
ondsbetwe
xample:
Silio Sihaso Illustr
electr
ccrystalco
rons
areinsulat
iumchlorid
(1
(1
saninsulat
artiallyfille
enlikeato
on,
Si
4outerele
ation belo
onshelland
Cha
sistsofposi
rs
e,NaCl
electrons
electrons
r
outershel
sarealway
trons
shows th
thusisina
ter1page13
tiveandne
2+8+1el
181ele
lsbondbys
scovalent(
t the cent
stableconfi
ativeions
ectron)
tron)
haringelect
.g.O2,N2,
r Si atom
guration
ronstofillt
)
has 8 elect
eoutersh
ons in its
lls
outer
8/13/2019 A MT Ch01 Introduction & Crystals
14/14
4. Mole
B E
5. Hybr
cularcryst
ondingforc
olecularcr
aalsbonds
xamples:
o CO2co Snow
dbonding
Group
IV
III
II
I
ls
sareVand
stalsarety
ystals(dryi
crystals
rystals(thi
Group
IV
V
VI
VII
Cha
erWaalsfo
icallymad
ce,lowtem
isnotase
ter1page14
rces(polari
upofmole
peraturesn
arateclassElement
Si
GaAs
ZnS
NaCl
ationforce
culesthata
eeded)
butamixtu
s)
reheldtog
reof2class
c
most
Mo
therbyVa
es)Bond
valent
lycovalent
stlyionic
ionic
der