Semiconductor physics

A Review of Physics of Semiconductors. Proceedings of the 13th International Conference (Rome 1976). Edited by F. G. Fumi. (North-Holland), 1976. [Pp. xiii + 1327.1 Price $95.00.     

Transport by single and few electrons in GaAs mesoscopic structures

A brief review is presented on some of the consequences of single electron transport in GaAs structures. Particular topics considered include noise and fluctuations in the ballistic regime where the quantised conductance imposes a limit on the magnitude of the random telegraphic signals and the consequences of single traps changing occupancy can be clearly observed. Results are also presented on the non-invasive detection of the Coulomb blockade and factors determining transport in the conductance minima are discussed. Thermo-electric effects in the blockade regime are discussed as these are complementary to studies of electrical transport and show that the thermopower oscillates about zero with a period corresponding to the removal of a single electron.     

Single-photon detection mechanism in a quantum dot transistor

We study the transport mechanisms in a quantum dot MODFET by tuning the localization induced by charge stored on the quantum dots with light. The temperature dependence of the resistivity of a macroscopic sample reveals a hopping transport when the dots contain an excess of electrons. The resistance of a mesoscopic sample however, which is capable of detecting single photons, exhibits a much weaker dependence upon temperature. This points towards source-drain tunnelling as a transport mechanism and is confirmed by a statistical analysis of the single-photon-induced conductance steps. The complexity of the conducting paths increases as the average hopping length reduces.     

Interfacial tension and spreading coefficient for thin films

We present a modified mathematical expression for the interfacial tension of very thin films. At large thicknesses the modified expression converges to the classic mathematical expression. We use this modified expression to derive an equation for the spreading coefficient as a function of film thickness. The spreading coefficient equation is then used to calculate the equilibrium thickness of a wetting liquid film for a "pancake drop". Our predictions agree with experimental data. The study is subjected to systems with van der Waals interactions only.     

Single-electron population and depopulation of an isolated quantum dot using a surface-acoustic-wave pulse

We use a pulse of surface acoustic waves (SAWs) to control the electron population and depopulation of a quantum dot. The barriers between the dot and reservoirs are set high to isolate the dot. Within a time scale of approximately 100 s the dot can be set to a nonequilibrium charge state, where an empty (occupied) level stays below (above) the Fermi energy. A pulse containing a fixed number of SAW periods is sent through the dot, controllably changing the potential, and hence the tunneling probability, to add (remove) an electron to (from) the dot.