GW1 - PHY491 Problem 1 Atoms(DUE Fri GROUP(Dated September...

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PHY491, Problem 1: Atoms (DUE: Fri 9/18/09) GROUP: (Dated: September 4, 2009) I. EXCITONS IN QUANTUM WELLS A quantum well is a semiconductor nano-structure in which carriers are confined in a plane. A photon absorbed by the semiconductor quantum well creates two charges. A negative charge, the electron, and a positive charge, the hole. The electron-hole system is bound by the Coulomb attraction and is very similar to an hydrogen atom, but with some differences: 1. The exciton is an ”hydrogen atom” in 2 dimensions. 2. The mass of the electron in the quantum well is 10 times smaller than the mass of an electron in the vacuum. 3. The mass of the hole is only two times bigger than the electron mass in the semiconductor (In the Hydrogen atom the proton is 1000 times bigger than the electron). 4. The Coulomb interaction energy between two charges q 1 and q 2 is V = q 1 q 2 ²r , (1) where ² 10 is the static dielectric constant of the semiconductor material. A. Preliminary estimates
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GW1 - PHY491 Problem 1 Atoms(DUE Fri GROUP(Dated September...

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