|M.Sc Student||Ori Scaly|
|Subject||Polariton Dispersion in Semiconducting Planer Microcavity|
|Department||Department of Physics||Supervisor||Professor Emeritus Cohen Elisha|
|Full Thesis text|
Semiconductors microcavities (MC) are structures made of two almost perfect mirrors with a spacer between them. The two mirrors are distributed Bragg reflectors. They form spatial confinement of the electromagnetic (EM) field: a MC-confined photon, whose energy depends on the refractive indices of the layer materials and on the spacing between the two Bragg mirrors. A quantum well (QW) embedded in the MC. It is designed so that the confined photon energy can be varied around the exciton energy. When the cavity confined photon energy is equal to the exciton energy there is a resonance interaction between them. This results in a Rabi splitting between the system eigenstates, which are mixed exciton - photon states (termed exciton-polariton).
In this work we studied two MC heterostructures. One is a mixed type-I type-II quantum well (MTQW) embedded in a MC. This structure consists of three QW's, two narrow and the middle wide. In the middle QW of the MTQW we create a 2 dimension electron gas (2DEG) by He:Ne laser illumination. The second is a modulation doped quantum well (MDQW) embedded in a MC. It consists of a QW with two silicon monolayers on each side, which act as donors and form 2DEG. The two MC structures were studied by reflection, photoluminescence (PL) and angle resolved PL spectroscopies that lead to a direct determination of the polariton dispersion. Like the Rabi splitting in the exciton polariton, a Rabi splitting accurse in the Fermi-edge polariton.
The main results of this study are: (a) Fermi-edge polaritons are formed when the confined photon energy is at resonance with the interband transitions at the Fermi energy of the 2DEG. We measured the Fermi-edge polariton dispersion. (b) The effective refractive index of the cavity structure is changing depending on the detuning point. (c) When the cavity mode energy is higher than of the Fermi-edge energy (namely above the resonance), the recombination time of e-h pair is shorter than the nonradiative relaxation time.