Pack Electrons in a Nano Box To Control Quantum Confinement
This development should make it possible to develop semiconductor non-linear devices which enable stable drive with low power consumption.
Researchers from the National Institute for Materials Science (NIMS) and Hokkaido University, have succeeded in controlling the few-particle quantum states of a gallium arsenide (GaAs) quantum dot, and changing its correlation energies.
The team was headed by Takashi Kuroda, Senior Researcher, and Marco Abbarchi, Researcher, of the Quantum Dot Research Center, National Institute for Materials Science. The team hopes this achievement will make it possible to develop semiconductor non-linear devices which enable stable drive with low power consumption.
Fig. 1: Atomic force microscope image of GaAs quantum dots used in this research.
In this research, gallium arsenide (GaAs) quantum dots were embedded in aluminum gallium arsenide (AlGaAs) by the droplet epitaxy method. This method was originally developed by NIMS.
A distinctive feature of the quantum dots, the length of the crystal lattice is perfectly matched between the guest and host materials, resulting in a clean quantum structure.
The scientists observed charged excitons by measuring the photon emission signals from single quantum dots. In particular, when the stabilization energy of charged excitons was compared with that of a quantum well structure of the same type of material, which was previously known to be ~1 meV, it was found to have a value more than 10 times larger.
This increase in many-body energy is due to a remarkable increase in the Coulomb force between the many-particle system which results from packing electrons in a 3-dimensional nano-space.
The researchers say that these results show, for the first time, the effect of confinement of a multi-electron state in a nano-space. From the viewpoint of applied technology, because electron correlation is also the source of diverse types of non-linear effect devices such as optical switching devices and lasers, if interaction intensity can be controlled using nanostructures, this can be expected to lead to the development of optical semiconductor devices which enable stable drive with low power consumption.
Further details of these results can be seen in the American scientific journal, Physical Review B, Vol. 82, Issue 20, Page 201301(R) (Nov. 15, 2010, DOI: 10.1103/PhysRevB.82.201301)
The paper is entitled “Energy renormalization of exciton complexes in GaAs quantum dots”, by M. Abbarchi et al.