Quantum Supercurrent Transistors in Silicon Quantum Wells Confined by Superconductor Barriers

Abstract

We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on-and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 10 21 cm -3 , represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The EPR studies show that these boron pairs are the trigonal dipole centres, B + -B -, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B 0 => B + -B -. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 10 11 cm -2 ) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on-and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transistor effect.

The effect of dipole boron centers on the electroluminescence of nanoscale silicon p+−n junctions

“…The negative-U pairing and the reconstruction of shallow acceptors into the trigonal dipole centers are accompanied by a formation of the correlation gap in the boron acceptor band [3,9]. The correlation gap distorts the density of states (DOS) which became different from its ordinary parabolic law.…”

“…It was previously found that the shallow boron acceptors under high concentration demonstrate the negative-U properties and can reconstruct into the dipole centers [1,2]. In the present work we study the heavily boron doped nanoscale silicon p + -n junctions which have been shown to represent the p-type silicon quantum well (Si-QW) confined by wide-band-gap heterobarriers on the Si (100) wafer [3]. The high concentration of boron, 5 × 10 21 cm -3 , in the heterobarriers is essentially higher than the critical concentration of the Mott transition [4] which seems have to cause a metallic-like conductivity.…”

“…The high concentration of boron, 5 × 10 21 cm -3 , in the heterobarriers is essentially higher than the critical concentration of the Mott transition [4] which seems have to cause a metallic-like conductivity. Nevertheless, the angular dependences of the cyclotron resonance spectra demonstrated that the p-type Si-QW contains the high mobility gas of 2D holes which is characterized by long momentum relaxation time of the heavy and light holes [2,3]. Thus, the momentum relaxation time of holes in the Si-QW appeared to be longer than in the best metal-oxide-semiconductor structures contrary to what might be expected from strong scattering by the heavily doped wide-band-gap heterobarriers.…”

“…Thus, the momentum relaxation time of holes in the Si-QW appeared to be longer than in the best metal-oxide-semiconductor structures contrary to what might be expected from strong scattering by the heavily doped wide-band-gap heterobarriers. To eliminate this contradiction the electron spin resonance (ESR) technique was applied for the studies of the boron centers [2,3]. The behaviour of the ESR spectra showed that the shallow boron acceptors are preferably form the trigonal dipole centers, B + -B -, which are caused by the elastic reconstruction along the <111> crystallographic axes as a result of the negative-U reaction: 2B o → B + + B -.…”

Correlation Between Arrhenius Equation and Binding Energy by X-ray Photoelectron Spectroscopy

“…There are many researches into SiOC films, because it is necessary to develop low dielectric (low-k) constant materials, as alternative to silicon dioxide film. Lowk SiOC film as interlayer dielectric material (ILD) has been used for the gate dielectric materials in FET (field effect transistor) devices, or as an insulator for passivation in solar cells [6][7][8][9]. The SiOC film was made by chemical vapor deposition (CVD) and spin on coating deposition (SOD), but there are some differences between the origins of the decreasing dielectric constant.…”