Sumários
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).
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.
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.
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.
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.