3 research outputs found
Lifetime enhanced transport in silicon due to spin and valley blockade
We report the observation of Lifetime Enhanced Transport (LET) based on
perpendicular valleys in silicon by transport spectroscopy measurements of a
two-electron system in a silicon transistor. The LET is manifested as a
peculiar current step in the stability diagram due to a forbidden transition
between an excited state and any of the lower energy states due perpendicular
valley (and spin) configurations, offering an additional current path. By
employing a detailed temperature dependence study in combination with a rate
equation model, we estimate the lifetime of this particular state to exceed 48
ns. The two-electron spin-valley configurations of all relevant confined
quantum states in our device were obtained by a large-scale atomistic
tight-binding simulation. The LET acts as a signature of the complicated valley
physics in silicon; a feature that becomes increasingly important in silicon
quantum devices.Comment: 4 pages, 4 figures. (The current version (v3) is the result of
splitting up the previous version (v2), and has been completely rewritten
Electric field reduced charging energies and two-electron bound excited states of single donors in silicon
We present atomistic simulations of the D0 to D- charging energies of a gated
donor in silicon as a function of applied fields and donor depths and find good
agreement with experimental measure- ments. A self-consistent field large-scale
tight-binding method is used to compute the D- binding energies with a domain
of over 1.4 million atoms, taking into account the full bandstructure of the
host, applied fields, and interfaces. An applied field pulls the loosely bound
D- electron towards the interface and reduces the charging energy significantly
below the bulk values. This enables formation of bound excited D-states in
these gated donors, in contrast to bulk donors. A detailed quantitative
comparison of the charging energies with transport spectroscopy measurements
with multiple samples of arsenic donors in ultra-scaled FinFETs validates the
model results and provides physical insights. We also report measured D-data
showing for the first time the presence of bound D-excited states under applied
fields
A hybrid double-dot in silicon
We report electrical measurements of a single arsenic dopant atom in the
tunnel-barrier of a silicon SET. As well as performing electrical
characterization of the individual dopant, we study series electrical transport
through the dopant and SET. We measure the triple points of this hybrid double
dot, using simulations to support our results, and show that we can tune the
electrostatic coupling between the two sub-systems.Comment: 11 pages, 6 figure