Chapter 9. Optoelectronic device

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

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

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

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

9. Optoelectronic device Spectrum of Light

9. Optoelectronic device LED with pn junction - +

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

9. Optoelectronic device

9. Optoelectronic device

9. Optoelectronic device

9. Optoelectronic device Structures of LEDs

9. Optoelectronic device

Table of LED materials 9. Optoelectronic device Semiconductor Substrate D / I Wavelength (nm) External efficiency Color GaAs Direct 870-900 10% Infrared AlxGa1-xAs (0 < x < 0.4) 640-870 5-20% Red to IR InGaN alloys GaN or SiC saphire 430-460 500-530 2% 3% Blue Green Sic Si; SiC Indirect 460-470 0.02% In0.49AlxGa0.51-xP 590-630 1-10% GaAs1-yPy (y<0.45) 630-870 <1% Red (N or Zn, O doping) GaP 560-700 Red, Orange GaP (Zn-O) 700 2-3% GaP(N) 565

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

9. Optoelectronic device

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

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

9. Optoelectronic device Paris Motor Show