Quantum transport relating to impurity quantum dots in silicon nanostructure transistor

Abstract

As the characteristic size of the transistor approaches to its physical limit, the effect of impurities on device performance becomes more and more significant. The number of impurities and the range of impurity fluctuation become very limited in channel space less than 10 nm, and ionized impurities in local nano-space can even exhibit quantum dot characteristics, providing two discrete levels for charge transport. The behaviour of carrier tunnelling through quantum dots induced by ionized impurities can reveal the abundant quantum information, such as impurity ionization energy, coulomb interaction energy, electron activation energy, orbital level filling, and spin of local electrons. Quantum transport properties are also different in different doping concentrations because whether the quantum states overlap depends on the impurity atom spacing. The silicon nanostructure transistors using impurity atoms as building blocks of quantum transport are also called dopant atom transistors, which are not only compatible with complementary metal oxide semiconductor (CMOS) technology, but also expected to be the basic components of quantum computing circuits in the future. So far, their operating temperature is relatively low due to the shallow ground state energy level of impurity atoms. It is of great significance to study the quantum transport properties in dopant atom transistors and to observe quantum effects among them at room temperature. In this article, the quantum transport properties in single, discrete and coupled impurity atomic systems are described in detail by combining Anderson localization theory and Hubbard band model. Quantum transport in a discrete impurity atomic system is not only controlled by gate voltage, but also dependent on temperature. The current transport spectrum in the coupled impurity atomic system reveals more complex quantum dot characteristics. Single atom transistor can regulate quantum transport only by one impurity atom, which represents the ultimate scale limit of solid state devices. In addition, the methods of improving the operating temperature of dopant atom transistors are also systematically introduced, thereby laying a foundation for their practical applications.