LEDs - Physics, Technologies and Tests (PH128-63-0)

SynopsisSince their invention in the early 1960s, light emitting diodes (LEDs) have enjoyed sustained rapid development in terms of efficiency, available emission spectrum, higher power, and application methods. To date, LEDs have become key component for wide range of applications; from telecommunications, to solid-state lighting, displays and sensing. The progress in LED technology in almost all areas of application is continuing at very rapid rate, ensuring that LEDs will continue to see accelerated growth in new and emerging markets, and will find use in applications that would have been considered impossible just a few years ago.

In this course, we will cover the fundamentals of LED, LED physics and technologies. In the first half of the course, we will review fundamental knowledge required for the understanding of LED design and operations. Topics that we will discuss in the first day will include semiconductor materials, absorption and recombination process in semiconductor, carriers in semiconductor, and simple diode theory.

In the second half of the course, we will focus on LED design, characteristics, fabrication, packaging and test and measurements. Current advances in white-light LEDs for solid-state lighting will also be discussed.

What You Will Learn

• Semiconductor materials
• Junction theory
• Light emitting device physics
• LED wafer structure and device designs
• Emission efficiency and light extraction
• LED packaging and characterization

Who Should AttendTechnicians, engineers, and managers involved in design, packaging and testing of LEDs including:

• Design engineers
• Process engineers
• Test engineers
• Yield analysis engineers
• Product engineers
• FA engineers
• Reliability engineering
• Application engineering

PrerequisiteParticipants should have a basic background and understanding of semiconductor technologies, device physics and some circuit design basics. Previous familiarity will be advantageous in maximizing the impact of the course on the participants. Nonetheless, these concepts will be quickly reviewed as needed.

Course MethodologyThis course is presented in an interactive classroom style utilizing lecture, open discussion, and examples.

Course Duration2 days, 9am - 5pm

Course Structure1) Overview

• History of LEDs
• Applications
• Course overview

2) Semiconductor light emitting materials

• Crystal lattices of semiconductors
• Bulk crystal growth
• Epitaxial growth

3) Semiconductor material properties

• Bandgap of semiconductor
• Charge carriers
• Carrier concentrations
• Drift carriers in electric and magnetic fields

4) Fundamentals of LEDs (Recombination processes)

• Radiation and non-radiative recombination
• Electron-hole recombination
• Excitations (low and high level)
• Luminescence decay
• Non-radiative recombination in the bulk and at surfaces
• Rate equations

5) Fundamentals of LEDs (Excess carriers in semiconductors)

• Optical Absorption
• Luminescence
• Carrier lifetime and photoconductivity
• Carrier Diffusion

6) Fundamentals of LEDs (Junction theory)

• Heterostructure
• P-N junction under equilibrium conditions
• Forward and reversed biased junctions; steady state conditions

7) LED basics

• Electrical properties
• Optical properties
• Emission efficiency and power efficiency
• Emission spectrum
• Radiation pattern
• Temperature dependence of emission intensity

8) High efficiency designs (Material and epitaxy structures)

• Double heterostrutures
• Quantum confined structures: Quantum-well, quantum-wire and quantum-dot
• P-n junction design
• Doping of active region and light confinement region

9) High efficiency designs (Device structures)

• Design of current flow
• Shaping of LED dies
• Textured semiconductor surfaces
• Anti-reflection coatins
• Flip chip packaging

10) High efficiency designs (Reflectors design)

• Metallic reflectors
• Total internal reflectors
• Bragg reflectors
• Omnidirectional refector

11) Packaging (low power packages)

• Protection against electrostatic discharge
• Thermal resistance of packages
• Epoxy encapsulants
• Chemical of Encapsulants
• Advanced encapsulant structures

12) Packaging (high packages)

• Thermal resistance
• Heatsink design
• Thermal electric cooler
• Advances in high power semiconductor laser packaging

13) Test & Measurements (Background & LED characteristics)

• Colorimetry: color purity
• LED in the chromaticity diagram
• Planckian sources and color temperature
• Color mixing and color rendering

14) Test & Measurements (other characteristics)

• Spectrum and spectral linewidth
• Polarization
• Light-current measurements
• Modulation characteristics: bandwidth, capacitance, current shaping, and eye diagram

15) White light LEDs

• Wavelength-converter
• UV-pumped white LEDs
• Calculation of power ratio
• Spectrum of white LEDs based on semiconductor converters