If you consider a quantum well (QW), what is the minimum energy barrier (difference between quantum well level and embedding layer bands) to effectively have the carriers two-dimensionally confined inside the QW, thus making it possible to detect 2D levels by optical techniques? Is the thermal energy KbT the only energy value to compare this energy barrier with (so at 10 K any barrier above 1 meV is enough)? Should I consider energy barriers only for separated carriers (e.g. only for electrons or holes) or should I consider the two carriers correlated?
To make things more clear: I have done calculation for confined levels into a QW solving the Schrodinger equation and I have found that QW levels are very close to band edges of embedding layers. Now I need to know if I should expect to see these levels by optical investigation (PL, PLE, PR) or if their energy difference is too low to have carriers recombine from 2D levels. From the model I can also get the wavefunction for confined carriers, but I still have not a clear picture what fraction of the carrier wavefunction should be in the QW for to detect it optically.
You should consider the energy barrier for electron or hole depending on which is the majority carrier in your case. If the contribution is quite comparable then you should go for both, I reckon.
Not being sure I understand the question, the barrier must be above the lowest bound state for the particle being considered. Your mentions of 2D baffle me. A well is 3D. For graphical purposes we often project it onto a single dimension. Would a 2D well be confining? Then if your intention is to detect the confined particle optically, what are the chances the photon will excite it either out of the well or to a higher bound state?
If your calculation shows that the energy level is close to the band edge, then I guess the question is how well the carrier can be confined. That will be temperature dependent. At different temperature, the fermi distribution of carriers will be different. Acting on the density of states will give you the carrier confinement. I guess, at low temperature, the PL measurement should give you some information on the energy levels.
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