1 / 19

OPTI 202L Lab # 12 – p-n Junctions: Photodiodes, Solar Cells LED’s, and Laser Diodes

OPTI 202L Lab # 12 – p-n Junctions: Photodiodes, Solar Cells LED’s, and Laser Diodes. Dr. Mike Nofziger Professor College of Optical Sciences University of Arizona.

donat
Télécharger la présentation

OPTI 202L Lab # 12 – p-n Junctions: Photodiodes, Solar Cells LED’s, and Laser Diodes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. OPTI 202LLab #12 – p-n Junctions: Photodiodes, Solar CellsLED’s, and Laser Diodes Dr. Mike Nofziger Professor College of Optical Sciences University of Arizona Dr. Mike Nofziger 2014

  2. Lecture #12 Outline:●Photodiodes—Physical Construction—Basic Properties—Basic Physics—Current Voltage Characteristics—Use in an Electrical Circuit●Solar Cells—Basic Properties●LED’s—Basic Properties Dr. Mike Nofziger 2014 Lecture 12

  3. Photodiodes—Physical Construction: “Official Symbol” A 40 Gb/s “Optical Receiver” !! Dr. Mike Nofziger 2014 Lecture 12

  4. ● p-n junction (p-side ≡ “anode”, n-side ≡ “cathode”)● Built-in electric field (depletion region) separates the electrons and holes (electrons → p-side, holes → n-side) ● Photons absorbed (ideally in or near the depletion region) create electron-hole pairs ● Built-in electric field separates the electrons and holes before they recombine, producing a photocurrent (electrons → n-side, holes → p-side)● I-V curve is very non-linear ● The photocurrent is linear with photon flux over 7-decades! ●Most common semiconductor material used to make photodiodes (for detection of visible light) is Silicon (Si). Photodiodes—Basic Properties: Dr. Mike Nofziger 2014 Lecture 12

  5. Photodiodes—Basic Physics: Dr. Mike Nofziger 2014 Lecture 12

  6. The “Shockley diode equation” Io is the reverse saturation current V is the voltage across the junction Photodiodes—Current-Voltage Characteristics: Photocurrent generated by irradianceEe(W/m2) Photocurrent generated by optical power ϕe (W) Dr. Mike Nofziger 2014 Lecture 12

  7. Photodiodes—Current-Voltage Characteristics: Dr. Mike Nofziger 2014 Lecture 12

  8. Photodiodes—Use in an Electrical Circuit: Operated at V = 0 “zero-bias”: Output is very linear over 7-decades of flux Operated at –V “reverse-bias”: Capacitance decreases, speed increases Operated at I≈0 “open-circuit”: The open-circuit voltage is logarithmic with flux: NOT the preferred way to operate a photodiode! Dr. Mike Nofziger 2014 Lecture 12

  9. Basics of Solar Cells:● A solar cell is a Photovoltaic (“PV”) detector: - is made of Silicon (not silicone!!) - absorbs light from ≈ 350nm – 1100nm - the absorption of light “frees up” electrons - This creates a voltage at the terminals of the cell (the “Open-Circuit” voltage)- If the cell’s terminals are shorted, the maximum current will flow (the “Short-Circuit” current)- If a load resistor is connected to the cell, a current will flow (the “Photocurrent”) Dr. Mike Nofziger 2014 Lecture 12

  10. Basics of Solar Cells:● The Power (Watts) that the cell can produce is given by:● Because of internal resistance in the cell, the maximum power you can generate is across a load resistance equal to the internal resistance.www.keithley.com Dr. Mike Nofziger 2014 Lecture 12

  11. “Sources of Light” • LED – Light Emitting Diode • – solid-state, semiconductor p-n junction • – GaAs, AlGaAs, GaP, AlGaInP, GaN, InGaN,etc. • – 3mm, 5mm, or 8mm dia. plastic packages • Low-Power LED’s • 1-20mA of electrical current • “on/off indicators” • High-power LED’s •  500mA to >1A • Lumileds, Osram, Cree • Lighting!! • Replace incandescent bulbs Dr. Mike Nofziger 2014 Lecture 12

  12. “Sources of Light” • LED – Light Emitting Diode Dr. Mike Nofziger 2014 Lecture 12

  13. “Sources of Light” • White-Light LED’s: General Approaches Reference Dr. Mike Nofziger 2014 Lecture 12

  14. “Sources of Light” • White-Light LED’s (3 phosphors, “tri-phosphor”) • – AlGaInN LED is the source of light • – emits light in the near-UV spectral region • – 380-430 nm • – 3 phosphor coatings on top • – Europium-based red and blue phosphors • – Copper and aluminum doped zinc sulfide • green phosphor • – Color-mixing more easily controlled to produce • a pure white light. • – Example: CREE Reference Dr. Mike Nofziger 2014 Lecture 12

  15. “Sources of Light” • White-Light LED’s (1 phosphor) • – GaN semiconductor LED is the source of light • – emits blue light 450 – 470 nm • – Yellow phosphor coating on top • – Cerium-doped YAG: Y3Al5O12:Ce3+ • – light is emitted by scintillation (no afterglow) Example: CREE Dr. Mike Nofziger 2014 Lecture 12

  16. “Sources of Light” • White-Light LED’s: TRENDS Reference Reference Dr. Mike Nofziger 2014 Lecture 12

  17. “Sources of Light” • White-Light LED’s: Applications vs. Dr. Mike Nofziger 2014 Lecture 12

  18. “Sources of Light” • White-Light LED’s: Applications Uses a CREE XM-L 1000 lumen LED Dr. Mike Nofziger 2014 Lecture 12

  19. Laser Diodes—LI Curve Dr. Mike Nofziger 2014 Lecture 12

More Related