Mechanism of Potential Profile Formation in Silicon Single-Electron Transistors Fabricated Using Pattern-Dependent Oxidation

Abstract

The origin of the potential profile in silicon single-electron transistors (SETs) fabricated using pattern-dependent oxidation (PADOX) is investigated by making use of the geometric structure measured by atomic force microscope (AFM), the bandgap reduction due to compressive stress generated during PADOX obtained using the first-principles calculation, and the effective potential method. A probable mechanism for the formation of the potential profile responsible for SET operation is proposed. The width reduction in the silicon wire region in the SET produces a tunnel barrier, while the compressive stress lowers the bottom of the conduction band through the bandgap reduction and forms a potential well corresponding to an island in the tunnel barrier.

Room temperature nanocrystalline silicon single-electron transistors

“…The increase in the barrier height in oxidized/ annealed SETs may be associated with the formation of oxide layers at the grain boundaries. We note that in crystalline silicon SETs formed by oxidized nanowires, 14 it is believed that the reduced width of the silicon nanowire region can produce potential barriers, while compressive stress at the SiϪSiO 2 interface can reduce the band gap, lowering the bottom of the conduction band and producing a potential well which forms the charging island. In our system, grainboundary potential barriers exist already, and it is difficult to ascertain the additional influence of stress associated with our oxidation and annealing process.…”

Room-Temperature Charge Stability Modulated by Quantum Effects in a Nanoscale Silicon Island

“…Note that Coulomb diamonds for each N are very symmetric with respect to the positive and negative drain biases, strongly indicating that a single ultra-small Coulomb island is formed at middle point of the channel and that its tunnel barriers with source and drain are nearly identical. 12 This rules out a possibility of that the observed Coulomb oscillations may be related to the possible dopant or defect which must be randomly formed. The charge stability data also exhibit that as the gate voltage is made less positive, the slope of each Coulomb diamond steeply increases, and the Coulomb diamond (for V G <3V) does not close.…”

“… -1  is also in the range of expected value for our dot size of 2nm by theoretical calculations. 12,13 Using these values we find that the addition charging energies of N=1  2, 2  3, and 3  4 are approximately 1 U  0.38eV, …”

Formation of strain-induced quantum dots in gated semiconductor nanostructures

“…20,21 Strain from oxidizing a mesa-etched nanowire has been shown to cause tunnel barriers, 22,23 at the ends of the nanowire. Strain from lattice mismatch is needed to explain the properties of resonant tunneling diodes in Si/SiGe nanowire heterostructures.…”