Chapter 3 Carrier Transport Phenomena ??????------

1
Chapter 3 Carrier Transport Phenomena??????-----
-

• ??????????????????

2
??????

• ????(carrier drift)
• ????(carrier diffusion)
• ???????generation and recombination process)
• ???????(thermionic emission process)
• ????(tunneling process)
• ????(impact ionization)

???
3
3.1 ????(drift)

• ??e0
• ?????,????(???n?????)?????????

????,??????,???????
?????
(????107cm/s)
4
??????????

• e?0?,????????????,???????????????????
• ???????

??????
??????
?c ???????(mean free time),??10-12s,??????(?10-5cm
)??vth?
5
??????????(?)

• ?? ????????n(mobility)
• ??,?????

????????
????????
????????p
6
Mobility?????c??

• ?c ???????,?????
• ????????,????????,?L???
• ??????????, ?I??
• ????,??????,??????????

7
????????

• ???dt???,????????dt/?c

??????????
??????,???????
8

• ????(1014cm-3)?????,?????????,??????,??????
• ?????????,?????????????,??????,??????????,???????
  ????,??????,??????

9
???????????????
??????,??????
?n gt ?p ????????????
10
3.1.2 Resistivity ?????????
????????,??????,??????? ???????
(????????)
????????????(??)
????
(??)
???
11
???????????

• ??????,?????????(????)?
• ????????Ec? EFi?Ev??y???(?????)

????????,???????????,???????????????,?????????????
??,????????????????????(drift current)?????,??????
????

• ?????,???????,????

12
??????
????
13
????
????
??
??????????
??,??????????
????????
?
??
???(conductivity)
14
???????
???????? N?n gtgt p P?p gtgt n
???????????
15
??????????

• ??????,?????
• N???????P?????(?????????????)

16
?????????

• ????,??????,???????,????????????,??????,?????,???
  ???
• ????,ni??,????,??????,??????
• ????,??????,????,???????,ni??,????????

Si
17
???????????
???????
CF?????,?d/s??(??d/s gt 20?,CF4.54)
18
(No Transcript)
19
3.1.3????(Hall Effect)

• ??????n??p????????????

??????? ??????????????????,?z????????,???????????
?p??????,?y0??????????,????????
??Ix???Bz??????????,VH??????
20
????(?)

• ?????,??????????

?????????,??????VH?
??
??????
?????????
???
????
?
21
?????????????
????
???????????????????????
??,n???????????????,?????????
22
??????????
??
??
??,n??????????(????)?
23
(No Transcript)
24
????

• ????????????????
• ???????????? x 0 ???????

dp/dx
dn/dx
?????
?????
??????
25
????

• ????????n(-l)?n(l),????

26
(No Transcript)
27
????????(????)
3-D
????????,?????ne??pe???????????????
28
Einstein Relation

• ??????,??????????
• ?????????????,??

Einstein ???
29
Einstein ???
??,???????????
30
(No Transcript)
31
3.3 ???????(?????)

• ??????,npni2?
• ??????,
• ?????????,?????
• ??????????????,??????,?????(generation)???(recombi
  nation)?????????????????

32
???????(?)

• ???????????????????????,?np?????ni2??????????????
  ,?np???ni2 ?
• ??(generation)?????????????
• ????????????,???????????
• ???????,????????,???????,????????,??????

33
??????(carrier injection)

• ????????pn????????,????????????????,??????????????
  (excess carriers)

• ????????????????,??????(low injection),???????????
  
• ??????,??????????????,???????

34
??????????

• ????(direct recombination)??????????????,??????
• ????(in direct recombination)??????????????,????
• ????(Surface recombination)
• ????(Auger recombination)

35
3.3.1???????-?????????????

• ?????????????,????????????,??????????
• ?????????????????,?????????

???,GthRth
???,????????
Gth???????????????
Rth???????????????
36
???????????
??????????????????p??
??????????????????p??
37
Direct Bandgap Indirect Bandgap

• ??????GaAs,?????????????,???????????????????,????
  ???????????????
• ??????Si,?????????????,??????????????????????,???
  ?????????

38
????????

• ???R??????????

??????
???
????????
????
??????
???????
39

• ????, ??

U??????
??????,?p?pn0ltltnn0,???????
????????
?
40
??????????
?????????,??????????,?t0??????,?????????????,????
?????
Rs
vL
41
?????????,??/?darltlt1,???????RSdRL,?????
42
(No Transcript)
43
(No Transcript)
44
3.3.2 ???????

• ????????????????????????????,????????????????,????
  ???????????(?????),????????(recombination
  centers)???(trap)?
• ??????????????,??????????
• ???????

45
?????????Shockley-Read-Hall????

• ???????????????????????
• ?????????????
• ????????????????,?????????????
• ?????????????

46
????????(???I)

• ?????? Ra??????????1-F(E)????
• ???
• ??????Rb??????F(E)????
• ???

???????
?????,???????????
????en?????
???? Ra Rb,?

??n????????
47
????????(?)
???????Ec,en??
??,
??????
?????
??????
????
48
?????

• ?????GL,???

??
??F,???
?????
Ra-Rb
(48)
49
???????????????,??
(49)
???????,??????
??????????
(50)
??????
????????????Nt???,???????????,???????????????
50
3.3.3 ????
?????,?????????????,????????????????-????,??????
?????????
51

?????????????,?????????????,?????????????????
52
?????

• ?????????????????????

53
3.3.4 ????(Auger recombination)

• ?????????????????????????
• ???????????????????????
• ?????????????

??????????
?
??????????
54
3.4 ?????

• ?????????????????????????????????????????????????
  ???????????

?????????,?dx????????????????Jn(x)??????Jn(xdx)??
????????????
?????????
55
?????(?)

• ????Jn(xdx)????????,???Adx

56
?????(?)

• ??????Poissons ???

57
???????????
58
3.4.1 ?????? A ,????,???

• ??????????????
• ?????pn(x0)pn(0)
• pn(x?8)pn0

N????
(??)
?????????????????
???
??????
59
B ,????,??W)
????????pn(x0)pn(0) pn(xw)pn0
?????????????????
??xw?????
60
3.4.2???????
??????,?????????????????qUs???????????,???????????
,????????????????????,?????????
??????????
??????????
?Slr?0?
Slr?8?,
61
3.4.3 ???-?????

• ????????D??????
• ?????,V1??????????,??1?????????,??????????2???????
  ?????????V2?

• ???????,???????Gp 0? ?e/?x 0(?????),???????

62
???-?????(?)
????????????
??????? ????????
V1?????,??????,?????
?????(V10)?,?????????????
?????????,??????????????? x ? x - ?pe ??
63
???-?????(?)
?????????? ??????V????
??? t ???? t1? t2,? t2 - t1 ?t
????
64
??????????
65
3.5 ???????(Thermionic emission process)
?????
???
????????????????,???????????,????????
66
(No Transcript)
67
3.6????(Tunneling process)
III
II

• ??????????,???(??)????(potential
  barrier)???????????????????????,????????,???????
• ?????(???????)???????(??),???????(?(x)),???????

I
??
????
68
????(?)
X 0
0 x d
X d
??
69
????(?)
??????? x o ? x d ??????? d?/dx 0,????????
??dgtgt1?,?????????,??
??d,????qV0????????????????????
70
3.7?????

• ????,vd??????(??????????????)
• ???????vd lt vth (107cm/s for Si) ??
• ?vd ?? vth,vd?????????

??????,????????
vs?????(107cm/s for Si) e0???(7103V/cm for
electrons 2104V/cm for holes)
71
?????(?)

• ????,????,????????????????

• ??????,????,???????????,?????????????????

72
??????????

• ??????????,?????????????????????????0.067m0??????0
  .55mo?

????(eltea),????????,??????,??????? ????(eltea),????
??,???????????,?????????
73
????,????????????
e gteb
74
?????????????????

• ??????????n1,?????????n2
• ??

????????
??????
75
?????????????????(?)

• ??

??1eagt?2eb
??????
????????????
76
????(Impact ionization)

• ???????,?????????,???????,???????????,????????????
  ???,??????????????????????????????????????????????
  ?,?????????????????,??????????????????????(??????)
  ?

77
????(Impact ionization)(?)

• ????1????????????????2?2,????????????????,????1??
  ????2?2???????,???????????????

???1??????????2??????, ????????????????
vs?????,vf?????
???????????????????????????????,???3.6eV
(3.2Eg),???5.0eV (4.4Eg)
78
???

• ??????n?????????????????????????????p????????????
  ????????????
• ?n??p??????????????104cm-1?????????,???????????31
  05V/cm?????????????4105V/cm?
• ????????GA?