Free-Carrier Plasmons as a Novel Tool in Semiconductor Physics

Abstract

It is demonstrated that free-carrier plasmons, being well defined collective excitations of the electron gas in the range of small wave vectors, can serve as a sensitive tool to investigate the optical processes related to the small momentum transfers. As an example the system HgSe:Fe is analysed both experimentally and theoretically. It is well known that the excitation of the free-carrier plasma in the light absorption process is possible only in the presence of defects breaking the translational invariance of the system. Due to the overall momentum conservation requirement there must exist a momentum source to make the photon absorption *This work is supported in part by CPBP 01.06.(141)

HgSe Based Mixed Crystals Doped with Fe Resonant Donors

“…This result fully confirms the earlier estimations which were based on the transport measurements. Α few papers (Szuszkiewicz et al [44] and references therein) were devoted to study relaxation time in the far infrared frequency range. The authors employed the fact that the plasmon related free-carrier absorption is sensitive to small momentum transfers.…”

The Dynamic Dielectric Function "Anomaly" for HgSe:Ga and HgSe:Fe

“…on the basis of transnmission measurements [7,8]. Preliminary results taken on the Fe-doped samples with relatively smaller iron concentration (NFe ranging from 5 x 10 1 8 cm-3 to 4 x 10 1 9 cm-3) correspond to the Fermi energy equal to about EF = 195 meV at low temperatures.…”

Influence of Impurity Charge Correlation on Free-Carrier Absorption

“…In calculations of the free-carrier absorption it is usually assumed that the impurities are randomly distributed in space. Recently, a detailed description of this absorption, taking into account possible spatial correlation in the distribution of charges on impurities, as well as collective plasma excitations has been formulated ( [1][2][3] and the references therein). The effect of impurity correlations is included via the structure factor S(q), which is equal to unity in totally uncorrelated systems.…”

“…The efficiency of plasmon generation in the free-carrier absorption should be therefore strongly reduced for the ordered systems. In particular, it has been suggested that plasmons, being well-defined collective excitations of the electron gas in the range of small wave vectors, can Serve as a sensitive tool in studying the space correlation of the Coulomb centers [3].…”