Graduate Attributes

1
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)

2
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

3
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

4
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

5
Insulators, Conductors, Semiconductors from
energy band structures
E
E
E
conduction band
conduction band empty
-
Band gap
partially-filled band
electron hole
Band gap
Forbidden region
Eg lt 5eV
Eg gt 5eV

valence band
valence band filled
Insulator Semiconductor Conductor
Si Eg 1.1 eV Ge Eg 0.75 eV GaAs Eg 1.42
eV
SiO2 Eg 9 eV
6
Electrons and Holes in Semiconductor
N type
P type
Intrinsic semiconductor Carriers come from
valence electron excitation
Key Effective control of charge carriers
Doped semiconductor
7
Carrier type, density mobility determined in
Hall measurements
Longitudinal conductance Jx ?Ex e(n?e
p?h)Ex Longitudinal resistivity ? 1/? The Hall
coefficient
If electron is the dominant carrier in the
material, then we have ? 1/? (en?e)-1, and
Carrier density n -(eRH)-1, and the mobility
?e - RH/?
8
Light Emission in Semiconductors
E
electron
conduction band
-
h?
Band gap
Electron-hole recombination

valence band
hole
Si Eg 1.1 eV, ? 1100 nm GaAs Eg 1.4
eV, ? 873 nm AlAs Eg 2.23 eV, ? 556 nm
Si indirect bandgap, ineffective GaAs direct
bandgap, effective
9
Basic semiconductor devices
C
E
p
n
p
n
p
B
Diode
Metal-semiconductor contacts
Bipolar transistor
G
G
SiO2
p
S
D
S
D
n
n
n
p
p
Inversion region
Depletion region
G
Metal-oxide-semiconductor FET (MOSFET)
Junction field-effect transistor (JFET)
10
Real Device Structures in IC
metal contacts
n
p
n
Diode
Bipolar transistor
MOSFET