1
EE 221A: Heterojunction Bipolar Transistors
Heterojunction BJT (HBJT) are made of heterojunctions, i.e. junctions between different
semiconductor materials. The success of HBJT relies on the growth techniques, such as
MBE or MOCVD to deposit well-contro
Qiming Shao, 304362944, [email protected], EE221A
Homework 1
(1)(a)
2mhh E EV
k2
E EV
, k
,
2mhh
dk
dE 2
2mhh
2mlh E EV
k2
, k
,
2mlh
dk
dE 2
2mlh
2
E EV
2
E EV EV
E EV
E EV
2m3 E EV EV
k2
, k
,
2m3
2
N hh E
4 k 2 dk 4 2mhh
DOShh E
2 for spin
3
V
h3
EE221A PS#3
(1) For a silicon pn junction with uniform dopings N A, D = 1 1017 cm 3 , and
Wn W p 0.5 m , plot the quasi-fermi levels when a forward bias of 0.5 V is
= =
applied.
( = = 10S, Dn 25cm 2 / s, D= 10cm 2 / s )
=
n
p
p
(2) Do the same if Wn W p 0
EE 221A - P.S. No. 1
Due October 14, 2015
(1) The valence band of silicon can be considered to have two approximately
spherical bands with their maximum at k=0 and with reciprocal effective
mass 1/mlh and 1/mll respectively. In addition, there is a split
EE 221A:
P H YSI CS OF SEM I CO N D U CTO R D EVI CES
The p-n Junction
P-n junctions are probably the most important devices to understand, because almost all
active devices involve the concept of p-n junctions.
A typical cross-section of a pn junction is
EE 221A:
Physics of Semiconductor Devices
Bipolar Devices
Bipolar devices are the first successful semiconductor active devices to make a real
impact in Integrated Circuits. Below is a typical cross-section of a bipolar junction
transistor (BJT).
E
N+ pol
EE 221A:
PHYSICS OF
SEMICONDUCTOR
DEVICES
Review of Semiconductor Physics
There are two classes of materials (solids): conductors and insulators.
Conductor:
The small D.C. conductivity at 0K is non-zero.
Insulator:
The small D.C. conductivity at 0K is zer
Metal Semiconductor Contact
Metal Semiconductor contacts are used in:
(1) Rectifying junctions such as in MESFETs, and Schottky diodes.
(2) Ohmic contacts: as all signals from the semiconductor devices eventually have to
be passed to the outside world, vi
EE 221A: PHYSICS OF SEMICONDUCTOR DEVICES
There are two classes of materials (solids): conductors and insulators.
Conductor:
The small D.C. conductivity at 0K is non-zero.
Insulator:
The small D.C. conductivity at 0K is zero.
All insulators have finite co
The p-n Junction
N
p+
P
|NA ND| (cm-3)
1020
1019
1018
1017
1016
0
N
P
0.1
0.2
0.3
x (m)
0.4
Note that a p-n junction actually has several three-dimensional
(geometric) features. The electrical characteristics is manily
determined by transport along the do
Bipolar (Junction) Transistor (BJT)
E
N+ poly
B
C
p+ poly
P+
P Intrinsic base
N+
N+
N- Collector
While BJT is two-dimensional in nature, intrinsic behavior mainly
one-dimensional between the dotted lines.
EC
EFn
VBE
EFp
EV
VCB
EFn
Under normal operation,
Qiming Shao, 304362944, EE221A, [email protected]
1. Answer:
For As atoms, Ec-Ed=0.053eV; For B atoms, Ea-Ev=0.045eV. (Ref: Chen, J. W., & Milnes, A. G. (1980).
Energy levels in silicon. Annual review of materials science, 10(1), 157-228.) For Au atoms, they c