Light emission due to the quantum confinement of carriers in silicon‐based nanostructures

Abstract

ABSTRACT:In the field of Si nanoscale ultralarge-scale integration, the quantum confinement effect is undesirable with respect to the device characteristics and performance because the carriers are entirely confined in nanoscale or low-dimensional structures. Significant efforts are being made with regard to the positive use of the quantum confinement effect in Si nanoscale structures. One such attempt is related to the use of Si optoelectronics and photonics for optical interconnections within a Si chip. In this study, the intrinsic electronic structures in the Si-based nanostructures with different dimensions and sizes as candidates for Si optoelectronics were investigated by the DV-X␣ molecular orbital calculation, which is advantageous to simulate the valence band structures for nanomaterials. We discuss the shift of a light emission peak to a higher energy due to the quantum confinement of carriers in the Si-based nanostructures, which depends on the sizes and numbers of structural dimensions, on the basis of the calculated results. Also, effect of doping of group IIIB and VB elements in the periodic table on the extrinsic electronic structures of the Si-based nanostructures were clarified by combining the Vienna ab-initio code for determining the relaxation structures around the dopants with the DV-X␣ method for simulating the valence band structures. The results obtained are useful as a measure of possibility of the Si-based nano-structured materials for optoelectronics.

Electronic Structures of X Level due to Indium-Carbon Dimers in Silicon

“…For the Si 71 H 60 , the band gap energy, defined as the energy difference between the HOMO and the LUMO, is 3.35 eV, which is far from the experimental band gap energy of 1.21 eV of crystalline Si at 0K. This large difference between the experimental and calculated band gap energies is due to quantum confinement effects resulting from the cluster size of nm [9]. In Fig.…”

“…There exists large difference in the ionization energy of between the calculated value in the cluster Si and the experimental value in crystalline Si both for doping of In and the InC dimer. This is also due to quantum confinement effects of the carriers, already mentioned [9]. We should point out from Fig.…”

A Formation Mechanism of X Level due to an Indium-Carbon Dimer in Silicon

“…This value is very different form the experimental value of 1.21 eV of Si crystal at 0 K. Quantum confinement effects resulting from the finite cluster size account for this large discrepancy in gap energy. [11] A dopant level within the energy gap, which was determined to be threefold degerenate and had T d symmetry, can be seen in Fig. 1(b) and 1(d) for the unrelaxed and relaxed In-Si 70 H 60 clusters, respectively.…”