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What is a wide bandgap semiconductor? Larger energy gap allows higher power and temperature operation and the generation of more energetic (i.e. blue) photons The III-nitrides (AlN, GaN and InN), SiC have recently become feasible. Other materials (like diamond) are being investigated.

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wide bandgap semiconductors
What is a wide bandgap semiconductor?

Larger energy gap allows higher power and temperature operation and the generation of more energetic (i.e. blue) photons

The III-nitrides (AlN, GaN and InN), SiC have recently become feasible. Other materials (like diamond) are being investigated.

What are they good for?

Wide Bandgap Semiconductors
slide2

WBG nitride for photonics

7

6.2eV

AlN

6

5

Band Gap Energy (eV)

4

UV

3.4eV

GaN

3

Visible light

2

1.95ev

IR

InN

1

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

o

Lattice Constant a (A)

market for iii nitride devices
Blue / UV solid state diodes and lasers

UV optical detectors

High power microwave devices

High power switches

High temperature devices

High density data storage devices

Additional Specialty Applications:

Surface acoustic wave (SAW) devices (for wireless communication)

High thermal conductivity substrates

Market for III-Nitride Devices
impact
Impact

Displays

Avionics and defense

Automotive industry

Information technology

(data storage)

Solid state lighting

Traffic lights

Wireless

communications

Electric power industry

Health care

the market for gan devices
The Market for GaN Devices

From Strategies Unlimited (1997)

Nichia estimates that the LD market alone will be worth $10B.

violet laser diode
Violet Laser Diode

Nichia announced commercial release of VIOLET LASER DIODE (Model No.NLHV500A) on October 1, 1999

Costs $2000 apiece.

possible new applications
Smart power controls

Smart cars

Smart manufacturing

Smart transportation

Smart house (energy management)

Information technology

Displays

Solid state lighting

Medicine

Defense

Possible new applications

SiC and GaN-

based switches

SiC and GaN-

based sensors

SiC and GaN-

non-volatile memories

GaN-based light emitters

GaN-solar blind

detectors

solid state lighting
GaN-based solid state display lighting is nearly an order of magnitude more efficient than incandescent lamps and twice as efficient for general lighting.

Practically does not require replacement.

Will affect the energy industry, construction, automotive, and avionics applications.

Solid State Lighting
compact power switches
Compact efficient power switches for power distribution, automotive, avionics, and industrial applications. These switches should allow energy savings up to 10%. This may allow us to avoid the deployment of new power plants, cut our dependence on imported oil, and improve reliability of power distribution in order to minimize blackouts during natural disasters. Compact power switches

Example of research by WBS faculty:

M. S. Shur, SiC Transistors, in "SiC Materials and Devices",

ed. Y. S. Park, (1998), Academic Press;

see also http://nina.ecse.rpi.edu/shur/GaN.htm

uv detectors and sources
UV sources and sensitive and fast UV detectors for applications in medicine, biology, chemical industry, and defense. UV detectors and sources

Example of research by WBS scientists:

M. S. Shur and M. A. Khan, GaN and AlGaN

Ultraviolet Photodetectors, Academic Press,

T. Moustakos and J. Pankove, Editors (1998)

see also http://nina.ecse.rpi.edu/shur/GaN.htm

flat panel high resolution low power displays for computer and medical applications
Flat panel, high-resolution low power displays for computer and medical applications.

8 mm

Prototypes:

Toshiba displays for billboards

Sharp displays for Pachinko

Example of research by WBS scientists:

M. S. Shur, M. D. Jacunski, H. Slade, and M. Hack,

Analytical Models for Amorphous-Silicon and Polysilicon

Thin-Film Transistors for High Definition Display

Technology, in Journ. Society for Information Display,

vol. 3, No. 4, pp. 223-236, Dec. (1995)

non volatile solid state memories
These memories will make hard drives obsolete and revolutionize banking, medical record-keeping, and information storage. Non-volatile solid state memories

After W. Xie, J. A. Cooper, Jr.,

M. R. Melloch,

J. W. Palmour, and C. H. Carter, Jr.,

" IEEE Electron Device Lett.,

15, 212 (1994).

flat panel high resolution low power displays for computer and medical applications1
Flat panel, high-resolution low power displays for computer and medical applications.

8 mm

Prototypes:

Toshiba displays for billboards

Sharp displays for Pachinko

wireless applications
Wireless Applications

AlN attractive for surface acoustic wave devices due to large piezoelectric effect. Sound velocity 10x materials currently used.

laser diode for mass data storage
Laser Diode for Mass Data Storage
  • Optical Data Storage Market will use over 300M LDs in 1999 (Compound Semicond., March 1999)
  • HD-DVD will use GaN or SHG laser; will dominate future market with 15GB capacity or greater
  • Market expects laser cost to be approx. $10 but current cost ~$2000.
light emitting diode led
Light-emitting Diode (LED)

First visible LED

Blue LED

traffic lights
Traffic Lights

One of the first applications of the new nitride semiconductor technology. The Green light uses 10% of the power and last more than 10x longer.

slide18

a Philips Lighting and Agilent Technologies joint venture that's changing the future of light. In the next century, LED-based lighting will quickly replace conventional lighting in a wealth of commercial, industrial and consumer applications. LumiLeds‘ LED-based solutions will bring irresistible value to lighting solutions of all kinds, earning us a leadership position in a fast-growing and lucrative marketplace. Our long-lasting, energy-efficient products will also improve the planet, by reducing waste and power consumption.

absorption and emission
Absorption and Emission

E

1

photon

in

photon out

E

o

stimulated vs spontaneous emission

Stimulated

Spontaneous

photon

in

photon out

Stimulated vs. Spontaneous Emission

E

1

E

o

stimulated vs spontaneous emission cont
Stimulated vs. Spontaneous Emission (Cont.)

Derived in 1917 by Einstein. (Required for thermal equilibrium was it was recognized that photons were quantized.)

However, a “real” understanding of this was not achieved until the 1950’s.

biased junction

photon out

p-type

Biased junction

Negative

bias

n-type

depleted region

(electric field)

history of lasers
First operating Laser in 1960 (Maser in 1958)

Simulated emission concept from Einstein in 1905

Townes (1964) and Schawlow (1981)

First solid-state injection Laser in 1962

First was Robert Hall but many competing groups

Year before he had argued it was impossible

History of Lasers
nichia laser diode
Nichia Laser Diode

10,000 hours

operation!

Epitaxial Lateral Overgrowth material

other applications for wide band gaps
High Power devices

Large band gap allows semiconductor to be used at high voltages

Generally larger band gap means stronger bonds so material can withstand higher currents and temperatures

High Temperature devices

Much smaller effect of thermal excitation of carriers

Tougher material

Other Applications for Wide band gaps
what are the hot research topics
How can the lifetime of the lasers be improved?

improved growth

improved substrates

improved devices

What is the role of defects?

Very high field transport

Quantum Confinement

What are the hot research topics?
quantum mechanics
Probability density given by

Schroedinger’s Equation:

where

Quantum Mechanics
quantum mechanics cont
Main point is that energy levels are Quantized!

Well defined energy level even at room temperature.

Quantum Mechanics (cont.)