Introduction to LEDs: How LEDs work + some points. Comparison with other sources of light. LED in communication. Blue &White LED technologies. How they are made? Their application? Brief about blue laser? Stands for light emitting diode. Semiconductor device: p-n junction emits incoherent narrow spectrum light (due to recombination in transition region near the junction.) Color of the emitted light depends on the chemical of the semiconducting material used. (Near-ultraviolet, visible or infrared.). | LEDs (Light Emitting Diodes) Supervisor: Dr. Khorasani Prepared by: Shirzad Malekpour Winter 1384 Introduction Introduction to LEDs How LEDs work + some points Comparison with other sources of light LED in communication Blue &White LED technologies How they are made Their application Brief about blue laser Light Sources in Electronics SOURCES LEDs Laser diodes LCD NEW Digital light processors (plasma) By TI LED Stands for light emitting diode. Semiconductor device: p-n junction emits incoherent narrow spectrum light (due to recombination in transition region near the junction.) Color of the emitted light depends on the chemical of the semiconducting material used. (Near-ultraviolet, visible or infrared.) LED Normally constructed of (Direct Gap): GaAs, GaAsP , GaP : Recombination light Si and Ge are not suitable because of indirect band. recombination result heat Structure and electroluminescence Band Gap Various band gaps different . | LEDs (Light Emitting Diodes) Supervisor: Dr. Khorasani Prepared by: Shirzad Malekpour Winter 1384 Introduction Introduction to LEDs How LEDs work + some points Comparison with other sources of light LED in communication Blue &White LED technologies How they are made Their application Brief about blue laser Light Sources in Electronics SOURCES LEDs Laser diodes LCD NEW Digital light processors (plasma) By TI LED Stands for light emitting diode. Semiconductor device: p-n junction emits incoherent narrow spectrum light (due to recombination in transition region near the junction.) Color of the emitted light depends on the chemical of the semiconducting material used. (Near-ultraviolet, visible or infrared.) LED Normally constructed of (Direct Gap): GaAs, GaAsP , GaP : Recombination light Si and Ge are not suitable because of indirect band. recombination result heat Structure and electroluminescence Band Gap Various band gaps different photon energies Ultra violet :GaN ev –infra-red: InSb ev Ternary&quarternary increasing number of available energies Example: 0 LED Radiation Patterns LED:Directional light source, maximum emitted power in the direction perpendicular to the emitting surface. typical radiation pattern shows that most of the energy is emitted within 20° of the direction of maximum light. Some packages for LEDs include plastic lenses to spread the light for a greater angle of visibility. Colors III-V materials Before II-VI (hard to have p-n junction) Solution: Nitrogen ZnSe (MBE grown) Progress: using multilayer hetero structures by MBE(Mulecular Beam Epitaxy) & OMVPE (organometalic vapor-phase epiaxy) (AlGaAs) - red and infrared (AlGaP) - green (AlGaInP) - high-brightness orange-red, orange, yellow, and green (GaAsP) - red, orange-red, orange, and .
