Spectroscopy of Free Carrier Excitations in Semiconductor Quantum Wells

Abstract

We have presented a review of recent results that highlight applications of the light scattering method in studies of quasi-two-dimensional electron systems. We have seen that the method can be used to measure the excitations associated with the free electron motion in the plane as well as that of the restricted motion normal to the plane. These features, in conjunction with the very advantageous option to measure spectra of collective and single particle excitations, make light scattering a very versatile spectroscopic tool. With the use of optical multichannel detection, and taking advantage of large resonant enhancements, it is possible to carry out experiments at very low laser power densities. This creates the possibility to study remarkable low temperature many-body phenomena, like the fractional quantization of the Hall effect, that are at the frontier of condensed-matter physics. We expect important applications in the area of time-resolved spectroscopy, where the method could reveal dynamical behavior of hot electrons. There is increasing interest in systems where the electrons have one-dimensional behavior (quantum wires) and also in zero-dimensional systems (quantum dots). We expect that inelastic light scattering, especially with the new techniques of micro-Raman spectroscopy, will play a prominent role in the elucidation of the intriguing properties of these novel semiconductor microstructures.