Abstract
It is shown that electron tunneling through a potential barrier that separates two quantum dots of germanium leads to the splitting of electron states localized over spherical interfaces (a quantum dot – a silicon matrix). The dependence of the splitting values of the electron levels on the parameters of the nanosystem (the radius a quantum dot germanium, as well as the distance D between the surfaces of the quantum dots) is obtained. It has been 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 has been found that the motion of a charge-transport exciton along a chain of quantum dots of germanium causes an increase in photoconductivity in the nanosystem. It is shown that in the QD chain of germanium a zone of localized electron states arises, which is located in the bandgap of the silicon matrix. Such a zone of local electron states is caused by the splitting of electron levels in the QD chain of germanium. Moreover, the motion of an electron in the zone of localized electron states causes an increase in photoconductivity in the nanosystem. The effect of increasing photoconductivity can make a significant contribution in the process of converting the energy of the optical range in photosynthesizing nanosystems. It has been found that comparison of the splitting dependence of the exciton level Eех(а) at a certain radius a QD with the experimental value of the width of the zone of localized electron states arising in the QD chain of germanium, allows us to obtain the distances D between the QD surfaces. It has been shown that by changing the parameters of Ge/Si heterostructures with germanium QDs (radius of a germanium QD, as well as the distance D between the surfaces of the QDs), it is possible to vary the positions and widths of the zones of localized electronic states. The latter circumstance opens up new possibilities in the use of such nanoheterostructures as new structural materials for the creation of new nano-optoelectronics and nano-photosynthesizing devices of the infrared range.
Highlights
In Ge/Si heterostructures with germanium quantum dots (QDs) are of the second type, the main electron level was in the silicon matrix, and the main level of holes was in the germanium QD [1,2,3,4,5,6,7,8]
When studying the optical properties of Ge/Si nanoheterostructures with germanium QDs, experimental work [1] was the first to reveal the spatial separation of electrons and holes, as a result of which electrons were localized above the QD surface, and holes moved into QDs
In Ge/Si heterostructures with germanium QDs, it was found in experimental works [1, 2] that lowtemperature optical absorption and photoluminescence spectra were caused by interband electron transitions from the valence band of germanium QD to the conduction band of the silicon matrix
Summary
In Ge/Si heterostructures with germanium quantum dots (QDs) are of the second type, the main electron level was in the silicon matrix, and the main level of holes was in the germanium QD [1,2,3,4,5,6,7,8]. If the distances D between the surfaces of QD of germanium in the nanosystem exceeded the value of Dc(2) , the exciton quasimolecule decayed into two excitons, in which electrons were localized above the spherical interface (QD – matrix), and the holes were in the valence band of germanium QD [6].
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