Quantum Dot Nanodevice with Electron-Lattice Coupling
- PDF / 101,248 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 209 Views
1108-A05-01
Quantum Dot Nanodevice with Electron-Lattice Coupling Karel Král Institute of Physics, Academy of Sciences of Czech Republic, v.v.i. Na Slovance 2, 18221 Prague 8, Czech Republic
ABSTRACT The electronic current-voltage characteristics of a nanotransistor is studied. The nanotransistor is assumed to consist of a quantum dot active region connected to the source and drain wires and also attached to a gate. The electric current is shown to be influenced by the coupling of electrons to the longitudinal optical phonons, namely, by the up-conversion of the electrons to the higher excited states in a quantum dot, due to a nonadiabatic effect of the lattice vibrations. In the nanotransistor with asymmetric source and drain contacts the up-conversion leads to a spontaneous electric current, or to a spontaneous voltage between the electrodes. We remind existing experiments which might be related to the effect considered.
INTRODUCTION The electronic energy relaxation in the materials of the type of GaAs is known to be strongly influenced by the interaction of electrons with the longitudinal optical (LO) phonons of the lattice vibrations. This is not only true in the bulk samples but also quite likely in the lowdimensional nanostructures, like quantum dots [1]. In the nano-systems the dissipation processes of the electrons are influenced not only due to the strength of the electron-phonon coupling, but also because of the geometrical shape of the nanostructure. This is because the charge carrier does not leave the scattering target (the LO phonons) going to infinity, but instead it reflects at the nanostructure boundary and returns back to the target, continuing in this way the irreversible process of multiple scattering. Due to the smallness of the system the efficiency of the scattering mechanism may be strongly enhanced by the multiple scattering nature of the processes. The multiple scattering of the electrons on the LO phonons in quantum dots, included in the electron kinetic equation in the self-consistent Born approximation to the electronic self-energy, leads not only to the fast electronic energy relaxation [2,3], but also it provides the effect of an up-conversion of electronic level occupation in quantum dots [2]. The up-conversion mechanism can explain e.g. the lasing of the quantum dot lasers from the higher excited electronic states, or the photoluminescence from SiO2-based nanoscale materials [4]. Recently the multiple scattering mechanism has also been shown to provide the explanation of the luminescence line shape of individual quantum dots [5], namely the form of a very narrow peak accompanied by a broader shoulder, usually at the low-energy side. Let us remark at this point that the appearence of this peculiar line shape has got the theoretical explanation so far only within the frame of the electron-LO-phonon multiple scattering scheme. Characterizing the theoretical approach we can briefly say that besides the self-consistent Born approximation to the electronic self-energy in the nonequilibr
Data Loading...
