Linear chains of Ge/Si quantum dots grown on a prepatterned surface formed by ion irradiation

Abstract

The growth of Ge nanoclusters on a prepatterned Si (100) surface formed by imprint lithography in combination with subsequent irradiation with Ge + ions is studied. The prepatterned surface presents a sys tem of parallel 10 nm wide grooves repeating with a period of 180 nm. Irradiation of the substrate was con ducted at two temperatures, room temperature (cold irradiation) and 400°C (hot irradiation). It is shown that, during epitaxy (550-700°C), the residual radiation defects located in the bulk under the grooves sup press the nucleation of Ge nanoclusters in the grooves. In the case of prepatterned substrates, from which imperfect regions are completely removed, nanoclusters grow in the grooves.

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

“…[10] that in a Ge/Si nanosystem with germanium QDs in the integral of average QD radii (6.4 eV, which was observed under experimental conditions up to room temperature. [1][2][3]7] Let us assume that the distances D between the surfaces of the QDs will be the same in the entire linear chain of germanium QDs on the substrate of the silicon matrix. [3,7] As a result, of electron tunneling through the potential barrier U(x) (6)- (8), which separates QDs, the exciton states E ex ðaÞ are splitted, forming a zone of localized electron states in a linear germanium QD chain.…”

“…It was found that in these nanostructures a photoluminescence signal in the infrared spectral region (0.20-1.14) eV was observed up to room temperature. [1][2][3][4][5][6][7] At low concentrations N QDs of germanium, when in linear chains, the average distance (%N À1/3 ) between the surfaces of the QD significantly exceeds the Bohr radius of the electron (a e ¼ 0.63 nm) in the silicon matrix, that is a e N 1=3 ( 1 (1) the interaction between QDs can be neglected. The optical properties of such nanosystems were mainly determined by the energy spectra of electrons and holes localized near the surface of single germanium QDs grown in a silicon matrix.…”

“…The optical properties of such nanosystems were mainly determined by the energy spectra of electrons and holes localized near the surface of single germanium QDs grown in a silicon matrix. [1][2][3][4][5][6][7][8][9][10][12][13][14] With the increase in the concentration N of germanium QD in linear chains, the average distance between the surfaces of the QD decreased. In nanostructures with large concentrations N of QDs at distances between the QD surfaces (about a e ), it is necessary to consider the interaction between the QD surfaces.…”

Spatially Indirect Excitons’ Spectroscopy in Germanium Quantum Dots

“…Quantitative estimation of the QD size corresponding to various exciton states can be carried out using the real nanosystem [1-3] containing the germanium QD with a radius a and permittivity  2  16. 3 , r e and r h are electron and hole distances from the QD centre [4,5]. In nanosystem, the main electronic level is located in silicon ma-trix, and the main hole level is in the QD.…”

“…In Ref. [3], heterostructures, which are linear germanium QD chains on silicon substrates, were obtained using the method of electron beam lithography. The average radii of QD of germanium did not exceed 30 nm.…”