Basics of Electrodynamics and Semiconductor Physics Flashcards
Explain the Lambert-Beer Law
Lambert’s Law states that the loss of light intensity when it propogates in a medium is directly proportional to intensity and path length.
Explain the relation between the complex refractive index, the dielectric function and the absorption coefficient.
Explain the difference between (i) insulator, (ii) metal [conductor] and (iii) semiconductor?
(i) Elements which do not allow any flow of electric charge i.e.
(ii) Elements which allow the flow of electric current through it by the application of voltage.
(iii) Elements which conductivity lie between insulator and conductor. We can do this by adding impurities.
Explain the differences between intrinsic semiconductor, degenerated semiconductor, n-doped semiconductor, and p-doped semiconductor.
Intrinsic semiconductors that are chemically pure, in other words, free from impurities are termed as intrinsic semiconductors. The number of holes and electrons is therefore determined by the properties of the material itself instead of the impurities.
A degenerate semiconductor is a semiconductor with such a high level of doping that the material starts to act more like a metal than a semicondcutor.
An n-type semiconductor is an intrinsic semiconductor doped with phosphorus
A p-type semiconductor is an intrinsic semiconductor doped with boron.
What is the effective mass of charge carriers?
In solid-state physics, a particle’s effective mass is the mass that it seems to have when responding to forces.
What’s the difference between drift and diffusion?
Drift current is the flow of current in a diode caused by an electric field.
Diffusion is the current caused by carrier diffusion as a result of a change in carrier concentration.
Explain the absorption of light in a semiconductor
Photons incident on semiconductor will be either:
i. reflected from the top surface
ii. absorbed in the material
iii. transmitted through the material
Describe the absorption of light through the energy of the photon and bandgap
Eph < Eg: pass through semiconductor as if it were transparent
Eph = Eg: enough energy to create an e-h+ pair are efficiently absorbed
Eph>Eg: strongly absorbed, but the excess photon energy is wasted as carriers quickly thermalise back down to the band edges
