Transcript development of voltage-tunable multicolor quantum well infrared

Overview of Semiconductor Technologies
• Key Semiconductor Technologies:
- Bulk silicon, SOI, III-V and II-VI semiconductors
• Economic Impacts of Semiconductor Industry
• Comparison of SIA Technology Road Map
Economic Impact of Semiconductor Industry
•
•
•
•
•
•
Global S.I. growth rate at 15%/year reaching $140 B in 97. This could reach
to $300 B by early 2000 due to the strong demand of communications
equipment and computers.
S.I. growth holds down inflation: S.I. price index: -4.5%/yr vs. +3%/yr for
the rest of economy.
Higher wages and lower inflation.
Faster technology diffusion (25%): Auto:60 yrs, Tel:35, TV:25, PC:13,
Internet:< 10 yrs.
Drivers of semiconductor market growth: declining prices and increasing
performance: price/DRAM bit reduced by 25 to 30%/yr, while IC complexity
double every 18 months (Moore’s Law).
Less’s Law: improvements in reliability have accompanied increases in chip
complexity:transistors/die increases from 2x103 in 1971 to 1.5x108 in 2003.
Current Status, Issues, and Trends in
Semiconductor Technologies
• Bulk Silicon Technologies:
- Scaled down submicron VLSIs
- Larger wafer size, 8, 10, 12”..
- Copper interconnects
• Silicon-On-Insulator (SOI) technologies:
- SIMOX and wafer bonding (WB).
- low power, low voltage, high-speed, and high density ULSIs. 3D IC’s
• III-V Semiconductor Technologies.
- LEDs, LDs, detectors, MESFETS, HBTs, HEMTs,
quantum effect devices (QWIPs).
- photovoltaic devices (solar cells) technology
- wide band gap and high temperature devices
(InGaN, GaN, AlGaN, SiC, diamond)
Comparison of the World
Semiconductor Industry
Comparison of SIA Technology Node
Introduction Projections in 94 vs. 97
94’ Roadmap
97”Roadmap
Min feature(mm)
Lithography
DRAM bits/chip
mP xstrs/chip
mP xstrs/cm2
98
97
0.25
248nm
256M
28M
7M
01
99
0.18
248/193
1G
64M
13M
04
03
0.13
193
4G
150M
25M
07
06
0.10
EUV
16G
350M
50M
10
09
0.07
EUV?
64G
800M
90M
New Materials for the New Millennium:
• Cu- metallization replaces Al-Cu interconnects for Si IC’s.
• New dielectric materials such as Ta2O5, BaSrTiO3 are being investigated to
replace SiO2, Si3N4 to handle the increase of DRAM density.
• New SOI technology to replace bulk Si technology for higher packing density,
higher speed and lower power consumption.
Technology Road Map for
Semiconductors
Delay Time vs. Power Dissipation for CMOS and
Other Devices
Exponential Increase of DRAM Density vs. Year
(Based on SIA Road Map)
Microprocessor Computational Power vs. Year
Silicon-On-Insulator (SOI) Technologies
•
•
•
•
•
•
Separation by Implantation of Oxygen (SIMOX) Process.
Wafer Bonding (WB) Process.
SIMOX WB Process.
Zone Melting Recrystallization (ZMR) Process
Epitaxial Lateral Overgrowth (ELO) Process
Fully Isolation of Porous Silicon (FIPOS) Process
Photovoltaic (PV) Market Analysis
• PV Market Growth Rate:
Solar cell module production average increase: 14% per year 90-97, and
production jumped by 38% in 1997 to 122 MWp. Growth rate is expected to
increase at a rate of 20%/year over the next 15 years with potential annual
module shipments of around 1,600 MWp (about $3billions per year by 2010) in
the year 2010.
• PV Markets:
- consumer electronic products (14%): calculators, watches, and lanterns...
- off-grid residential power systems (35%): cottages, rural village homes..
- off-grid industrial power system (33%) : telecom.repeaters..
- off-grid connected PV systems(18%):government and/or utility demons.
Key PV Technologies
•
•
•
•
•
•
•
Single crystal Si solar cells.
Poly Si solar cells.
a- Si thin film solar cells.
Ribbon Si solar cells.
CdTe thin film solar cells.
CIS (CuInSe) thin film solar cells.
III-V semiconductor (GaAs, InP, GaInP..) solar cells
- single and multi-junction solar cells
• Concentrator solar cells.
III-V Semiconductor Technologies
•High-speed, high-frequency, quantum effect, and optoelectronic
devices:
- HBTs, HEMTs, MESFETs.
- Quantum dot, quantum wire, and quantum well infrared
photodetectors and lasers. Superlattice heterostructure devices
- LEDs, LDs, solar cells.
•III-V materials:
- GaAs/AlGaAs, InGaAs/GaAs, InGaAs/AlGaAs grown on GaAs
- InGaAs/InAlAs, InGaAsP/InP grown on InP
- InP, InAs, InSb, InGaSb, GaInN, GaN, AlN
II-VI and Wide Band Gap Semiconductors
•II-VI semiconductors:
- ZnSe, ZnS, CdS, CdTe: Solar cells, LEDs, LDs
- HgCdTe, CdZnTe, PbSnTe.
•Wide Band Gap Semiconductors: ( 2.5 < Eg < 6.5 eV)
- Diamond, SiC, AlN, GaN, AlGaN: high-temperature
transistors (HBTs, MESFETS..), high- power devices,
UV detectors and laser diodes.
A Bright Future for Blue/Green LEDs
(Highly luminous III-V nitride based LEDs)
Color
Wavelength (nm)
Violet
Blue
< 430
430 - 490
(GaN,InGaN/AlGaN LEDs)
Green
490 - 560
(InGaN/AlGaN or ZnSe, GaP LED)
Yellow
560 - 590
(AlInGaP LEDs)
Orange
Red
(AlGaAs LEDs)
590 - 630
> 630
Chapter 1 Classification of Solids
•
The Crystal Systems and Bravais Lattices.
•
The Crystal Structure and The Unit Cell.
•
Miller Indices and Crystal Planes.
•
The Reciprocal Lattice and Brillouin Zone.
•
Types of Crystal Bindings
•
Defects in Crystalline Solids
Classification of Solids
Based on geometrical aspects:
- 7 crystal systems and 14 Bravais lattices
•
Based on binding energy:
- metallic, ionic, covalent, and molecular crystals
Na, K; NaCl; C, Si, Ge; Ar, He, Ne
• Based on electrical conductivity: metals, semiconductors, insulators.
- metals : s > 104; semiconductors: 10-4 <s < 104; insulators: s < 10-5 (ohm-cm)-1
• Based on atomic arrangements (periodicity):
- single crystalline solids: atomic arrangements are ordered with periocity
extending through the entire crystal lattice.
- polycrystalline solids: short range ordered within grain and separated by grain
boundaries.
- amorphous solids: no short range ordered, atomic arrangements are highly
irregular. (glass, oxides,…)
Bravais Lattices
Seven lattice systems and fourteen Bravais lattices
•
Triclinic
•
Monoclinic
•
Orthorhombic
•
Tetragonal
•
Trigonal
•
Hexagonal
•
Cubic
b1  b2  b3
a b  g
b1  b2  b3
a = b = 90 o  g
b1  b2  b3
a = b = g = 90 o
b 1 = b2  b 3
a = b = g = 90 o
b 1 = b2 = b 3
a = b = g  90 o
b 1 = b2  b 3
a = b = 90 o , g = 120o
b 1 = b2 = b 3
a = b = g = 90 o
simple
simple, base-centered
simple, base-centered
body-centered; F.C.C
simple, body-centered
simple,
simple,
simple, body-centered
F. C. C.
Unit Cell of a Bravais Lattice
Unit Cell of a Bravais Lattice
z
b3
b
g
b2
a
y
b1
x
r (n1,n2,n3) = r (0,0,0) + R
R = n1b1 + n2b2+ n3b3
is the translational basis vector
The Bravais Lattice
• A space lattice is a concept introduced first by Bravais, and
hence the Bravais lattice. The various arrangements of unit
cells in a crystalline solid can be achieved by means of space
lattice.
• A parallelepiped unit cell of a Bravais lattice is formed by 3
non-coplanar basis vectors b1, b2,, and b3 with different lengths
and angles between them. There are 14 Bravais lattices in space
lattice as shown in Fig.1.1.
• A unit cell formed by 3 non-coplanar primitive basis vectors
with lattice points only located in the vertices of the
parallelepiped unit cell is called primitive cell.
• The translational basis vector can be used to generated any
lattice points in the space lattice, which can be described by:
- r (n1, n2, n3) = r(0, 0, 0) + R
where R = n1b1 + n2b2 + n3b3; n1, n2, n3 = 0, 1, 2, 3……
The Crystal Structure
• The crystal structure is formed by attaching an atom or
a group of atoms to the lattice point of a Bravais lattice.
• Figure 1.3 (a) shows a 2-D space lattice, and Fig.1.3(b)
shows a 2-D crystal structure with atoms attached to
each lattice point.
• Four important crystal structures for semiconductors
are shown in Fig.1.4. These are: (a) diamond structure
(Si, Ge, GaAs), (b) Zinc-blende structure (III-V, II-VI
semiconductors), (c)Wurtzite (III-V, II-VI), and
(d) hexagonal closed-packed (HCP) structure.
Miller Indices
• The orientation of a crystal plane can be determined by 3
integers, h, k, l, known as the Miller indices, which are
defined by:
hh’ = kk’ = ll’
(1)
where h’, k’, l’, represent the intercepts of a particular
plane on the three crystal axes (x,y.z) in units of lattice
constant a. h, k, l, are the three smallest integers that
satisfy eq.(1).
Example: if h’, k’, l’ = a, 2a, 2a, then the smallest h, k, l
that satisfy eq.(1) is (2,1,1), and the plane is called (211)
plane.
Reciprocal Lattices and Brillouin Zone
• The reciprocal lattice is a geometrical construction which allows one to
relate the crystal geometry directly to the electronic states and the symmetry
properties of a crystal in the reciprocal space. It’s the Fourier transform of
the direct (space) lattice in the reciprocal space, which can be expressed as:
exp(iK.R) = 1
where: K = hb1* + kb2* + lb3*; R = n1b1 + n2b2 +n3b3
R.K = 2p(n1h+n2k+n3l) = 2p  = 0 1 2 
• In a reciprocal lattice, a set of reciprocal basis vectors b*1, b*2 , b*3 can be
defined in terms of the three translational basis vectors b1, b2 , b3 in the direct
space:
b*1 = 2p(b2xb3)/|b1.b2xb3|
Vd = |b1.b2xb3|
b*2 = 2p(b2xb3)/|b1.b2xb3|
b*3 = 2p(b2xb3)/|b1.b2xb3|
Vr* = |b1*.b2*xb3*| = 8p3/Vd