Microwave Properties of 2D CMOS Compatible Co-Planar Waveguides Made from Phosphorus Dopant Monolayers in Silicon

Low-dimensional microwave interconnects have important applications for nanoscale electronics, from complementary metal–oxide-semiconductor (CMOS) to silicon quantum technologies. Graphene is naturally nanoscale and has already demonstrated attractive electronic properties, however its application to electronics is limited by available fabrication techniques and CMOS incompatibility. Here, the characteristics of transmission lines made from silicon doped with phosphorus are investigated using phosphine monolayer doping. S-parameter measurements are performed between 4–26 GHz from room temperature down to 4.5 K. At 20 GHz, the measured monolayer transmission line characteristics consist of an attenuation constant of 40 dB mm−1 and a characteristic impedance of 600 Ω. The results indicate that Si:P monolayers are a viable candidate for microwave transmission and that they have a.c. properties similar to graphene, with the additional benefit of extremely precise, reliable, stable, and inherently CMOS compatible fabrication

2D-3D crossover in a dense electron liquid in silicon

Doping of silicon via phosphene exposures alternating with molecular beam epitaxy overgrowth is a path to Si:P substrates for conventional microelectronics and quantum information technologies. The technique also provides a new and well-controlled material for systematic studies of two-dimensional lattices with a half-filled band. We show here that for a dense ($n_s=2.8\times 10^{14}$\,cm$^{-2}$) disordered two-dimensional array of P atoms, the full field angle-dependent magnetostransport is remarkably well described by classic weak localization theory with no corrections due to interaction effects. The two- to three-dimensional cross-over seen upon warming can also be interpreted using scaling concepts, developed for anistropic three-dimensional materials, which work remarkably except when the applied fields are nearly parallel to the conducting planes.Comment: 9 pages, 4 figures, supplementary informatio

Intersubband dynamics below the optical phonon energy for single and coupled quantum well systems

We have made direct measurements of the intersubband lifetime in single GaAs quantum wells below the optical phonon energy at 36 meV, At low temperatures and excitations LO phonon emission is inhibited and acoustic phonon emission dominates; a sharp cross-over exists between the two regimes. Rate equation calculations have been performed for the single well samples with no fitting parameters and these agree well with experiment. The calculations have been extended to coupled quantum wells and we find that by careful tuning of the well widths the LO phonon rate can be tuned by up to an order of magnitude

Lifetime measurements of group V donor rydberg states in silicon at THz frequencies

We have measured the T1 lifetimes of Rydberg states of phosphorus and arsenic in silicon at THz frequencies using the FELIX pulsed free electron laser. Our results show the dominant decoherence mechanism is lifetime broadening