1. Chapter 9. Optoelectronic device

2. Optoelectronic Diodes
9. Optoelectronic device
Optoelectronic Diodes
PD (PhotoDetector)
  photo-to-electrical conversion to detect or determine
  Information about the photo-energy
Solar cell
  photo-to-electrical conversion to produce electrical power
LED (Light Emitting Diodes) and LD (Laser Diodes)
  electrical energy into photo-energy
⇒ Applications
  - bar code reader
  - digital disk reader
  - laser printer
  - optical communications
  - communication satellites
  - display

3. 9. Optoelectronic device
What is the LED LED (Light-emitting Diode) Typical pn-junction device used under forward bias Depending on the semiconductor material used in the light emitting layer(active layer), the wavelength of the emitted light can be anywhere within the range from visible to infrared

4. Three requirements for LEDs
9. Optoelectronic device
Three requirements for LEDs
ⅰ) direct semiconductor
ⅱ) To be visible, 0.4μm<λG<0.7μm
    → 1.77 eV< EG<3.10 eV
ⅲ) easy to form pn junction diode

5. Energy bandgap Semiconductor with direct bandgap : GaAs, InP, ZnSe …
9. Optoelectronic device
Energy bandgap
Semiconductor with direct bandgap : GaAs, InP, ZnSe …
Semiconductor with indirect bandgap : Si, Ge, GaP …
recombination center, phonon emission
some photon emissions are possible

6. 9. Optoelectronic device
Spectrum of Light

7. 9. Optoelectronic device
LED with pn junction - +

8. Mechanism of Light Emitting
9. Optoelectronic device
Mechanism of Light Emitting
When the junction is biased in forward direction

9. 9. Optoelectronic device

10. 9. Optoelectronic device

11. 9. Optoelectronic device

12. 9. Optoelectronic device
Structures of LEDs

13. 9. Optoelectronic device

14. Table of LED materials 9. Optoelectronic device Semiconductor
Substrate
D / I
Wavelength
(nm)
External
efficiency
Color
GaAs
Direct
10%
Infrared
AlxGa1-xAs
(0 < x < 0.4)
5-20%
Red to IR
InGaN alloys
GaN or SiC
saphire 2% 3%
Blue
Green
Sic
Si; SiC
Indirect
0.02%
In0.49AlxGa0.51-xP
1-10%
GaAs1-yPy (y<0.45)
<1%
Red
(N or Zn, O doping)
GaP
Red, Orange
GaP (Zn-O)
700
2-3%
GaP(N)
565

15. Applications Indicator lights LCD panel backlight
9. Optoelectronic device
Applications
Indicator lights
LCD panel backlight
Fiber optic data transmission

16. 9. Optoelectronic device

17. 9. Optoelectronic device
Research is the transformation of money to knowledge.
Innovation is the transformation of knowledge to money.

18. Paris Motor Show : Solar Car
9. Optoelectronic device
Paris Motor Show : Solar Car

19. 9. Optoelectronic device
Paris Motor Show