15. Photons in Semiconductors
15. Photons in Semiconductors
Semiconductor materials Semiconductor materials
) x ( )
L x
( + = ψ ψ
IV
Si GaAs
Semiconductor materials Semiconductor materials
Selected Elemental and Ill-V Binary Semiconductors
Their Bandgap Energies Eg, at T = 300 K, Bandgap Wavelengths λg = hc /Eg, Type of Gap (I = Indirect, D = Direct)
UV
Optical fiber communication
D. Generation, Recombination, Internal QE D. Generation, Recombination, Internal QE
Electron-Hole generation Electron-Hole recombination
radiative recombination : photons
nonradiative recombination : lattice vibrations (phonons), Auger process
Internal quantum efficiency
the ratio of the radiative electron-hole recombination rate to the total (radiative and nonradiative) recombination rate (r).
Or, in radiative and nonradiative lifetimes
GaN 20 ns 0.1 ns 0.1 ns 0.005
INTERACTIONS OF PHOTONS WITH ELECTRONS AND HOLES INTERACTIONS OF PHOTONS WITH ELECTRONS AND HOLES
formation of an electron and a hole at some distance from each other but which are nevertheless bound together by their mutual Coulomb interaction.
Absorption coefficient of bulk semiconductors Absorption coefficient of bulk semiconductors
Si GaAs
Conditions for Absorption and Emission Conditions for Absorption and Emission
Absorption (PD)
Spontaneous Emission
(LED)
Induced Emission
(LD)
Spontaneous emission rate and Absorption coefficient Spontaneous emission rate and Absorption coefficient
Spontaneous Emission Spectral Density in Thermal Equilibrium (direct band-band transition)
Absorption Coefficient in Thermal Equilibrium (direct band-band transition)
Refractive index
Refractive index
Quantum confinement structures Quantum confinement structures
Why?
