The Splitting of Electron States in Ge/Si Heterostructure with Germanium Quantum Dots

Abstract

It is shown that electron tunneling through a potential barrier that separates two quantum dots (QDs) of germanium leads to the splitting of electron states localized over spherical interfaces (QD–silicon matrix). The dependence of the splitting values of the electron levels on the parameters of the nanosystem (the radius a of germanium QDs, as well as the distance D between the surfaces of the QDs) is obtained. It is shown that, the splitting of electron levels in the QD chain of germanium causes the appearance of a zone of localized electron states, which is located in the bandgap of silicon matrix. It is found that the motion of a charge‐transport exciton along a chain of QDs of germanium causes an increase in photoconductivity in the nanosystem.

Theory of spatially indirect excitons in nanosystems containing double semiconductors quantum dots

“…[17]), electrons e( 1) and e( 2) with effective masses (1) were localized over the spherical surfaces of QD(A) and QD(B) in potential wells caused by Coulomb attraction (x) (6) electrons and holes (where x is the electron distance from the surface of the QD).An exciton quasimolecule with an increase in the distance D between the surfaces of the QD (condition (3) is satisfied), so that , decayed into two SIEs [17]. Such SIEs appeared when the photon with the energy smaller than the width of the bandgap = 1.17 eV) of the silicon matrix was absorbed by the nanosystem [15][16][17][18][19].With an increase in the QD radius a (so that a ≥ 22.2 nm), SIE withenergy (a) turned into 2D SIE with energy (a) = = 2 [15,16]. In this case, is the binding energy of the 2D SIE and = 2.6 nm.In refs.…”

“…In this case, is the binding energy of the 2D SIE and = 2.6 nm.In refs. [15,16] and [18,19], the energy of the SIE state (a)was measured from the bottom of the conduction band of the silicon matrix ( = ). The potential barrier ))…”

“…separating double QDs was caused by the Coulomb attraction (x) (6) of electrons e( 1) and e(2) to their holes. Electrons e( 1) and e(2) localized above the spherical surfaces of double QDs can tunnel through the potential barrier U(x) (17), (18).…”

“…(2) (a). In [18,19], using the semiclassical approximation, an expression was obtained that describes the splitting Δ (a, D) = ( (1) (a) (2) (a)) of the SIE level =  …”

“…In the Ge/Si heterostructure, at distances D between the QD surfaces exceeding the splitting of electron states localized over spherical interfaces (QD is a silicon matrix) occurred.This splitting of electron states was caused by the tunneling of electrons through a potential barrier separating the double QDs. In this case, a band of localized electronic states appeared in the band gap of the silicon matrix [18,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The mini-review considers the appearance of in the Ge/Si heterostructure SIEs and exciton quasimolecules depending on the distance D between the surfaces of germanium QDs.It was shown that the binding energy of the singlet ground state of an exciton quasimolecule took on a gigantic value, exceeding the binding energy of a biexciton in a silicon single crystal by almost two orders of magnitude.It was found that, as a result of the splitting of electron levels in the chain of germanium QDs, a band of localized electron states appeared.…”