Sumários

Interaction processes between light and matter. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics.

29 Setembro 2023, 14:30 • José Figueiredo

Interaction processes between light and matter. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics.
Photon allowed energy levels: Bose-Einstein distribution. Energy level occupation of an atom: Boltzmann distribution. Conduction and valence bands of semiconductors as a two-energy level system. Spontaneous emission, absorption, and stimulated emission. Spontaneous emission by an atom. Stimulated emission and absorption are processes induced by the presence of light. Einstein A and B coefficients. Enhanced spontaneous emission - Purcell effect. Thermal light and Boltzmann distribution. Thermal light – blackbody radiation Forms of luminescence. Single photon photoluminescence. Multiple photon photoluminescence. Up-conversion fluorescence. Light scattering processes: Rayleigh, Raman, Stokes, anti-Stokes, Brillouin, and non-resonant scattering. Photon interactions of with charge carriers in bulk semiconductors. Conditions for photon absorption and emission in semiconductors. Photon absorption in indirect semiconductors; Thermalization. Photon emission in indirect semiconductors. Electroluminescence in thermal equilibrium: example GaAs emission. Injection electroluminescence. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics. LED Materials. Typical LED structures. Typical LEDs - p-n heterojunctions. Basic LED Principle. Forward biased non-degenerately doped pn junction. Forward biased degenerately doped pn junction. Emission Spectrum. LED spectral linewidth. Dependence of the emission peak and linewidth on temperature. GaN LEDs are generally Multiple Quantum Wells (MQWs).

Interaction processes between light and matter. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics.

29 Setembro 2023, 13:30 • José Figueiredo

Interaction processes between light and matter. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics.
Photon allowed energy levels: Bose-Einstein distribution. Energy level occupation of an atom: Boltzmann distribution. Conduction and valence bands of semiconductors as a two-energy level system. Spontaneous emission, absorption, and stimulated emission. Spontaneous emission by an atom. Stimulated emission and absorption are processes induced by the presence of light. Einstein A and B coefficients. Enhanced spontaneous emission - Purcell effect. Thermal light and Boltzmann distribution. Thermal light – blackbody radiation Forms of luminescence. Single photon photoluminescence. Multiple photon photoluminescence. Up-conversion fluorescence. Light scattering processes: Rayleigh, Raman, Stokes, anti-Stokes, Brillouin, and non-resonant scattering. Photon interactions of with charge carriers in bulk semiconductors. Conditions for photon absorption and emission in semiconductors. Photon absorption in indirect semiconductors; Thermalization. Photon emission in indirect semiconductors. Electroluminescence in thermal equilibrium: example GaAs emission. Injection electroluminescence. Electroluminescence due to injection of carriers. Light emitting diode structures and characteristics. LED Materials. Typical LED structures. Typical LEDs - p-n heterojunctions. Basic LED Principle. Forward biased non-degenerately doped pn junction. Forward biased degenerately doped pn junction. Emission Spectrum. LED spectral linewidth.

Pn Junctions properties.

25 Setembro 2023, 15:00 • José Figueiredo

Pn Junctions properties. Band Diagram of a pn Junction under open circuit. pn junction forward bias. pn Junction reverse bias. Properties of the pn junction. Laws of the Junction. Minority and majority Carriers. Diffusion Current. Recombination and Total Current. The diode equation. Typical current-voltage (I-V) characteristics of Ge, Si and GaAs Diodes. pn junction Dynamic Resistance and Capacitance. Forward Bias Dynamic Resistance and Capacitance. pn Junction Depletion Capacitance.

Semiconductor Structures. Homojunctions and Heterojunctions, Bandgap Engineering.

25 Setembro 2023, 14:00 • José Figueiredo

Semiconductor Structures. Homojunctions and Heterojunctions, Bandgap Engineering. pn junction.Semiconductor Structures. Homojunctions and Heterojunctions, Bandgap Engineering. Pn homo- and heterojunctions. Semiconductor pn heterojunction. Typical GaAs/AlGaAs LEDs pn heterostructure. Semiconductor Band-gap engineering and quantum confinement. Quantum Wells e Multiple Quantum Wells. Energy levels in the quantum well. A GaAs quantum well. Single and Multiple Quantum Wells in LEDs and Lasers.
 

Review of semiconductor materials and semiconductor electrical and optical properties.

22 Setembro 2023, 14:30 • José Figueiredo

Review of semiconductor materials and semiconductor electrical and optical properties. 
Semiconductor doping. Extrinsic Semiconductors: n-Type. Extrinsic Semiconductors: p-Type. Compensation Doping. Example of a doping process - ion implantation.  Degenerate Semiconductors. Example: Fermi levels in semiconductors. Example: Conductivity of n-Si. Direct and Indirect. Bandgap Semiconductors. Electrons in Semiconductor Crystals. Electron and hole effective mass in semiconductors. Electron’s crystal momentum. Energy (E) vs. electron’s crystal momentum (k). E-k diagrams and direct and indirect bandgap semiconductors.