No abstract

Using the effective mass and rectangular potential approximations, the theory of electron dynamic conductivity is developed for the plane multilayer resonance tunnel structure placed into a constant electric field within the model of open nanosystem, and oscillator forces of quantum transitions within the model of closed nanosystem. For the experimentally produced quantum cascade laser with four-barrier active band of separate cascade, it is proven that just the theory of dynamic conductivity in the model of open cascade most adequately describes the radiation of high frequency electromagnetic field while the electrons transport through the resonance tunnel structure driven by a constant electric field.

No abstract

Using the Feynman-Pines diagram technique, the energy spectrum of localized quasi-particles interacting with polarization phonons is calculated and analyzed in the wide range of energies at the finite temperature of the system. It is established that the general model of the system, besides the bound states known from the simplified model with an additional condition for the operator of quasi-particles number, contains the new bound states even for the systems with weak coupling. The contribution of multi-phonon processes into the formation of renormalized spectrum of the system is analyzed. The reasons of the appearance, behaviour and disappearance of separate pairs of bound states depending on the coupling constant and temperature are revealed.

Subject classification: 63.22.+m; 73.21.La; S8.11 Different types of electron (hole) ground energy level renormalization due to confined (L) and interface (I) phonons in a spherical quantum dot embedded in a semiconductor medium are investigated on the example of b-HgS/CdS nanoheterosystem. It is shown that for all QD sizes the shift of the ground energy level (D) is generally caused by the interaction of electron and confined phonons of the dot (L 0 ) and of the medium (L 1 ). The contribution of interface phonons (I + , I --) to the magnitude D is comparable with the contribution of L-phonons only at small QD radii (it is three times smaller). For all QD radii the interaction with all phonons through all states of the continuous spectrum gives a one order smaller contribution to D than the interaction through the states of the discrete spectrum. When the QD radius increases the I-phonon contribution decreases and the L-phonon one increases, consequently, the total shift becomes closer to its magnitude in bulk HgS crystal.