04-09-2012, 03:48 PM
LIGHT EMITTING DIODE – Design Principles
[attachment=33343]
OBJECTIVES:
To learn the basic design principles of LED
To relate properties of semiconductor material to the principle of LED
To be able select appropriate materials for different types of LED
To be able to apply knowledge of band gap engineering to design appropriate materials for a particular LED
To acknowledge other materials that can and have been used in LED
By the end of this lecture you must be able to …
Draw a typical construction of an LED.
Explain your drawing.
State all the issues regarding the materials selection of an LED.
State all of the possible answers regarding your materials issues.
Explain band gap engineering
Explain the isoelectronic doping in GaAsP system
State examples of materials that emit, UV, Vis, IR lights
Luminescence is the process behind light emission
Luminescence is a term used to describe the emission of radiation from a solid when the solid is supplied with some form of energy.
Electroluminescence excitation results from the application of an electric field
In a p-n junction diode injection electroluminescence occurs resulting in light emission when the junction is forward biased
Injection Luminescence in LED
Under forward bias – majority carriers from both sides of the junction can cross the depletion region and entering the material at the other side.
Upon entering, the majority carriers become minority carriers
For example, electrons in n-type (majority carriers) enter the p-type to become minority carriers
The minority carriers will be larger minority carrier injection
Minority carriers will diffuse and recombine with the majority carrier.
For example, the electrons as minority carriers in the p-region will recombine with the holes. Holes are the majority carrier in the p-region.
The recombination causes light to be emitted
Such process is termed radiative recombination.
[attachment=33343]
OBJECTIVES:
To learn the basic design principles of LED
To relate properties of semiconductor material to the principle of LED
To be able select appropriate materials for different types of LED
To be able to apply knowledge of band gap engineering to design appropriate materials for a particular LED
To acknowledge other materials that can and have been used in LED
By the end of this lecture you must be able to …
Draw a typical construction of an LED.
Explain your drawing.
State all the issues regarding the materials selection of an LED.
State all of the possible answers regarding your materials issues.
Explain band gap engineering
Explain the isoelectronic doping in GaAsP system
State examples of materials that emit, UV, Vis, IR lights
Luminescence is the process behind light emission
Luminescence is a term used to describe the emission of radiation from a solid when the solid is supplied with some form of energy.
Electroluminescence excitation results from the application of an electric field
In a p-n junction diode injection electroluminescence occurs resulting in light emission when the junction is forward biased
Injection Luminescence in LED
Under forward bias – majority carriers from both sides of the junction can cross the depletion region and entering the material at the other side.
Upon entering, the majority carriers become minority carriers
For example, electrons in n-type (majority carriers) enter the p-type to become minority carriers
The minority carriers will be larger minority carrier injection
Minority carriers will diffuse and recombine with the majority carrier.
For example, the electrons as minority carriers in the p-region will recombine with the holes. Holes are the majority carrier in the p-region.
The recombination causes light to be emitted
Such process is termed radiative recombination.