Control of the ionization state of three single donor atoms in silicon

Abstract

By varying the gate and substrate voltage in a short silicon-on-insulator trigate field effect transistor we control the ionization state of three arsenic donors. We obtain a good quantitative agreement between 3D electrostatic simulation and experiment for the control voltage at which the ionization takes place. It allows us observing the three doubly occupied states As − at strong electric field in the presence of nearby source-drain electrodes.1 arXiv:1403.1079v1 [cond-mat.mes-hall] Mar 2014Although doping has always been the cornerstone of semiconductor technology, devices have started to enter a new era where a single dopant can be used for new (quantum) functionalities: charge and spin qubits, single-electron pumps, turnstiles and transistors 1,2 .Thin silicon-on-insulator (SOI) devices are particularly attractive for the implementation of donor-based functionalities, because they offer very good control of the transverse electric field in the channel. This electrostatic property is at the core of the Metal-OxideSemiconductor Field-Effect Transistors (MOSFETs) but is also crucial to address dopants individually and to control their electronic wavefunctions and couplings. These abilities are prerequisite for dopant-based applications.In this work we study both experimentally and with simulations how 3 arsenic donors are charged in a nanoscopic MOSFET when the substrate, gate and drain voltages are varied with respect to the grounded source. The ionization state of each donor is separately read out by detecting its corresponding resonance in the source-drain current. The ionization state of each donor -As + , As 0 and As − -is individually controlled at low temperature by the electric field. The scalability of a compact system of a few tunable shallow donors beyond the previously studied cases of 1 3-7 and 2 donors 4,8 is then shown.In our small MOSFETs -in the 10 nm range size-dopants are not isolated in the channel but see a complex electrostatic environment which includes other donors in the channel and in the source-drain (S-D) as well as offset charges in the gate stack. This environment should be considered cautiously. First other donors in the channel may result in the many-body problem of a Coulomb glass. For lightly doped semiconductors, long range fluctuation effects dominate over the immediate environment charges 9,10 . Fortunately in our short MOSFETs the interaction between donors is screened by the S-D. We can therefore treat the charging of a specific donor taking the ionization state of the others as constant over a large range of gate voltages, and therefore assign each line in the stability diagram to a specific dopant atom (see Fig.1).The ionization of donors at the graded edges -or extensions-of the source and drain is also explicitly considered in our simulation in a mean-field approach which neglects Kondo Once the potential landscape has been computed as a function of V b and V g , we have added a few bulk-like impurities in the channel at positions r i , and have tracke...

Charge Dynamics and Spin Blockade in a Hybrid Double Quantum Dot in Silicon

“…S2), where D 0 is the neutral donor and D − the anion. Moreover, we observe this transition very close to the threshold, as expected [22].…”

Spatially resolved resonant tunneling on single atoms in silicon

“…We have computed the charging energy as the energy difference between the two peaks, assuming for simplicity that α is a linear function of the energy: we obtain E C =17 meV. This is a lower value as compared to the bulk (53 meV) but in agreement with reference [36] and with the charging energies observed in MOSFET structures [18,21,22], where interfaces, leads (tip, substrate) and electric fields [41] have a crucial role. We can finally note that the tip-induced state, highlighted by the upper black dotted line in Fig.…”

Two-electron states of a group-V donor in silicon from atomistic full configuration interactions

“…The reservoir is particularly important in scanning tunneling experiments when the highly doped silicon layer is located 10-20nm away from the donor [33,34]. For MOS-like devices, the device contacts are in proximity to the donor too and ideally the image charges in contacts must be accounted for as well, which have been ignored in this work [35]. Metallic and oxide interfaces close to an electron affect the electrostatics of the system and screen the electron-electron repulsions, thus lowering the two electron energies of the system.…”