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16

The problem is that you are confusing light intensity with energy of a single photon. The photoelectric effect requires a certain energy per photon to work. But low light intensity just means fewer photons come - you can actually see the grain if the conditions are too dark: every pixel can get ~10 photons or less... and yet still, each photon that comes has ...


4

It is a thermal effect, the corresponding "force" is a so called stochastic force and not a fundamental force, but rather an effective description of entropic effects. Having a temperature causes the charge carriers to move about randomly, and therefore they tend to move from regions with high concentration to regions with low concentrations. At first it is ...


1

To delve more deeply into the origin of the various bands, you should go look at the literature where these bands are calculated. The classic reference for silicon and germanium is Energy-Band Structure of Germanium and Silicon: the k.p Method. Since this is still fairly early in band structure calculations, they do walk you through how the Hamiltonian is ...


1

If you're looking for a strict derivation of the effective mass equation, check out S. Datta, Quantum phenomena. Reading, Mass.: Addison-Wesley, 1989. What he does is take the full Schrödinger equation with the periodic potential, and write it in the Bloch state basis. He then writes the effective mass equation in the plane wave basis. By comparing the ...


1

The first case you mention where you just sandwich GaAs inside AlGaAs is worked out in page 66 of Semiconductor Nanostructures. By adding a doping layer you control the carrier density and with that the resistivity. Like you say, it's necessary to draw the electrons away from the doping layer using attraction to the smaller-gapped GaAs. This creates bound ...


1

Regarding your question on sandwiching GaAs between two AlGaAs barriers: If you do this for a narrow quantum well (like you sketched above), the electron wavefunction protrudes into the barrier quite a bit. As the barrier material is a ternary alloy, the electrons are exposed to alloy scattering. This is simply due to the fact that Ga and Al atoms are ...


1

It might help to just look at the vacuum level, and think of how the structure reaches equilibrium. In your first picture, electrons will start to flow from right to left, towards the lower fermi level. This will charge the left side negatively, and leave positive charge on the right side. Therefore the vacuum level will curve on both sides, with a U ...



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