Graduate Attributes(Southern Cross University, Australia)
The graduates of the University are expected to develop the following
during their programmes:
Intellectual rigour
Creativity
Ethical understanding, sensitivity, commitment
Command an area of knowledge
Lifelong learning --- ability of independent & self-directed learning
Effective communication and social skills
Cultural awareness
(From: S. Yeo, CDTLink, NUS, July 2004)
Importance of Materials Processing
All electronic devices & systems are made of materials in
various combinations
Raw materials are far from the final electronic products
Semiconductor materials (e.g., Si, Ge, GaAs, GaN...) used for
devices must be of extremely high purity and crystalline order
Desirable Device Qualities
Strong functionality
Reliable, long lifetime
Low cost, high energy efficiency
Small volume, light weight...
Examples: your notebook PC, mobile phone…
All these require high precision and efficient materials processing technologies
Real Materials and their Processing
Particles, lines and rigid bodies vs. real materials
Material-specific properties determine the function
and processing details of a material
Comprehensive knowledge of materials processing
requires ~ 5-10 years of learning and practice
Advantage and role of physics students
Insulators, Conductors, Semiconductors from energy band structures
E
valence band filled
conduction band empty
Forbiddenregion Eg > 5eV
Bandgap
E
conduction band
Eg < 5eVBandgap
+
-electronhole
E
valence band
partially-filledband
Insulator Semiconductor ConductorSi: Eg = 1.1 eVGe: Eg = 0.75 eVGaAs: Eg = 1.42 eV
SiO2: Eg = 9 eV
Electrons and Holes in Semiconductor
Intrinsic semiconductor Carriers come from valence electron excitation
Doped semiconductor
N type
P type
Key: Effective control of charge carriers
Carrier type, density & mobility determined in Hall measurements
)(
22
eh
eh
x
yH npe
np
BJ
ER
Jx
B VH
Ey
Longitudinal conductance:Jx = Ex = e(ne + ph)Ex
Longitudinal resistivity: = 1/
The Hall coefficient:
If electron is the dominant carrier in the material, then we have:
= 1/ = (ene)-1, and ne
RH
1
Carrier density: n = -(eRH)-1, and the mobility: e = - RH/
Light Emission in Semiconductors
E
conduction band
Bandgap
+
-
electron
valence band
Si: Eg = 1.1 eV, = 1100 nmGaAs: Eg = 1.4 eV, = 873 nmAlAs: Eg = 2.23 eV, = 556 nm
hole
hElectron-hole recombination
Si: indirect bandgap, ineffectiveGaAs: direct bandgap, effective
Basic semiconductor devices
p n
Diode
p n
Bipolar transistor
pE C
BMetal-semiconductor
contacts
p+
p+
nS D
G
G
Junction field-effect transistor (JFET)
p
n+ n+
G SiO2
Depletion region
Metal-oxide-semiconductor FET (MOSFET)
Inversion region
S D
Real Device Structures in IC
MOSFET
Bipolar transistorDiode
n
n+ p
metal contacts