One consequence of the continued downwards scaling of transistors is the reliance on only a few discrete atoms to dope the channel, and random fluctuations of the number of these dopants is already a major issue in the microelectonics industry. While single-dopant signatures have been observed at low temperature, studying the impact of only one dopant up to room temperature requires extremely small lengths. Here, we show that a single arsenic dopant dramatically affects the off-state behavior of an advanced microelectronics field effect transistor (FET) at room temperature. Furthermore, the ionization energy of this dopant should be profoundly modified by the close proximity of materials with a different dielectric constant than the host semiconductor. We measure a strong enhancement, from 54meV to 108meV, of the ionization energy of an arsenic atom located near the buried oxide. This enhancement is responsible for the large current below threshold at room temperature and therefore explains the large variability in these ultra-scaled transistors. The results also suggest a path to incorporating quantum functionalities into silicon CMOS devices through manipulation of single donor orbitals.
We have developed nano-scale double-gated field-effect-transistors for the study of electron states and transport properties of single deliberately-implanted phosphorus donors. The devices provide a high-level of control of key parameters required for potential applications in nanoelectronics. For the donors, we resolve transitions corresponding to two charge states successively occupied by spin down and spin up electrons. The charging energies and the Lande g-factors are consistent with expectations for donors in gated nanostructures.
The inter-device mismatch and intra-device temporal instability in the nanoscale CMOS circuits is examined from a unified point of view as a static and dynamic parts of the variability con-cerned with stochastic oxide charge trapping and de-trapping. This approach has been benchmarked on the recent evidence of the radiation-induced increase of inter-transistor mismatch in 60 nm ICs. A possible reliability limitation in ultrascale circuits concerned with the single or a few charged defect instability is pointed out and estimated.
We analyze the electron spin relaxation rate $1/T_1$ of individual ion-implanted $^{31}$P donors, in a large set of metal-oxide-semiconductor (MOS) silicon nanoscale devices, with the aim of identifying spin relaxation mechanisms peculiar to the environment of the spins. The measurements are conducted at low temperatures ($T\approx 100$~mK), as a function of external magnetic field $B_0$ and donor electrochemical potential $μ_{\rm D}$. We observe a magnetic field dependence of the form $1/T_1\propto B_0^5$ for $B_0\gtrsim 3\,$ T, corresponding to the phonon-induced relaxation typical of donors…
We explore phonon-mediated quantum transport through electronic noise characterization of a commercial CMOS transistor. The device behaves as a single electron transistor thanks to a single impurity atom in the channel. A low noise cryogenic CMOS transimpedance amplifier is exploited to perform low-frequency noise characterization down to the single electron, single donor and single phonon regime simultaneously, not otherwise visible through standard stability diagrams. Single electron tunneling as well as phonon-mediated features emerges in rms-noise measurements. Phonons are emitted at high …
Silicon-On-Insulator nanowire transistors of very small dimensions exhibit quantum effects like Coulomb blockade or single-dopant transport at low temperature. The same process also yields excellent field-effect transistors (FETs) for larger dimensions, allowing to design integrated circuits. Using the same process, we have co-integrated a FET-based ring oscillator circuit operating at cryogenic temperature which generates a radio-frequency (RF) signal on the gate of a nanoscale device showing Coulomb oscillations. We observe rectification of the RF signal, in good agreement with modeling.
We report finite-bias characteristics of electrical transport through phosphorus donors in silicon nanoscale transistors, in which we observe inelastic-cotunneling current in the Coulomb blockade region. The cotunneling current appears like a resonant-tunneling current peak emerging from the excited state at the crossover between blockade and non-blockade regions. These cotunneling features are unique, since the inelastic-cotunneling currents have so far been reported either as a broader hump or as a continuous increment of current. This finding is ascribed purely due to excitation-related ine…
For nanoscale CMOS applications, strained-silicon devices have been receiving considerable attention owing to their potential for achieving higher performance and compatibility with conventional silicon processing. In this work, an analytical model for the output current characteristics (I-V) of nanoscale bulk strained-Si/SiGe MOSFETs, suitable for analog circuit simulation, is developed. We demonstrate significant current enhancement due to strain, even in short channel devices, attributed to the velocity overshoot effect. The accuracy of the results obtained using our analytical model is ver…
The nuclear spin bath (NSB) dynamics and its quantum control are of importance for the storage and processing of quantum information within a semiconductor environment. In the presence of a carrier spin, primarily it is the hyperfine interaction that rules the high frequency NSB characteristics. Here, we first study the overall coherence decay and rephasings in a hyperfine-driven NSB through the temporal and spectral behaviors of the so-called Loschmidt echo (LE). Its dependence on the NSB size, initial polarization, and coupling inhomogeneity are separately investigated, which leads to a simp…
The advanced nanoscale integration available in silicon complementary metal-oxide-semiconductor (CMOS) technology provides a key motivation for its use in spin-based quantum computing applications. Initial demonstrations of quantum dot formation and spin blockade in CMOS foundry-compatible devices are encouraging, but results are yet to match the control of individual electrons demonstrated in university-fabricated multi-gate designs. We show here that the charge state of quantum dots formed in a CMOS nanowire device can be sensed by using floating gates to electrostatically couple it to a rem…
Donor impurity spins in silicon-28 are highly competitive qubits for upcoming solid-state quantum technologies, yet a proven scalable strategy for multi-qubit devices remains conspicuously absent. These CMOS-compatible, atomically identical qubits offer significant advantages including 3-hour coherence ($T_2$) lifetimes, as well as simultaneous qubit initialization, manipulation and readout fidelities near $\sim\!99.9\%$. These properties meet the requirements for many modern quantum error correction protocols, which are essential for constructing large-scale universal quantum technologies. Ho…
Fundamental properties of two electrostatically interacting single-electron lines (SEL) are determined from a minimalistic tight-binding model. The lines are represented by a chain of coupled quantum wells that could be implemented in a mainstream nanoscale CMOS process technology and tuned electrostatically by DC or AC voltage biases. The obtained results show an essential qualitative difference with two capacitively coupled classical electrical lines. The derived equations and their solutions prove that the two coupled SET lines can create an entanglement between electrons. The results indic…
Semiconductor devices continue to press into the nanoscale regime, and new applications have emerged for which the quantum properties of dopant atoms act as the functional part of the device, underscoring the necessity to probe the quantum structure of small numbers of dopant atoms in semiconductors[1-3]. Although dopant properties are well-understood with respect to bulk semiconductors, new questions arise in nanosystems. For example, the quantum energy levels of dopants will be affected by the proximity of nanometer-scale electrodes. Moreover, because shallow donors and acceptors are analogo…
The possibility of quantum computing with spins in germanium nanoscale transistors has recently attracted interest since it promises highly tuneable qubits that have encouraging coherence times. We here present the first complete theory of the orbital states of Ge donor electrons, and use it to show that Ge could have significant advantages over silicon in the implementation of a donor-based quantum processor architecture. We show that the stronger spin-orbit interaction and the larger electron donor wave functions for Ge donors allow for greater tuning of the single qubit energy than for thos…
We study the low temperature electrical transport behaviour of a silicon single electron transistor. The island and leads are defined by patterned phosphorus doped regions achieved by ion implantation through a polymer resist mask. In the device a 50 nm diameter island, containing ~600 donors and having a metallic density of states, is separated from source and drain leads by undoped silicon tunnel barriers. The central island and tunnel barriers are covered by a surface gate in a field effect transistor geometry allowing the coupling between the leads and island to be controlled. Coulomb bloc…
Temperature is a fundamental parameter in the study of physical phenomena. At the nanoscale, local temperature differences can be harnessed to design novel thermal nanoelectronic devices or test quantum thermodynamical concepts. Determining temperature locally is hence of particular relevance. Here, we present a primary electron thermometer that allows probing the local temperature of a single electron reservoir in single-electron devices. The thermometer is based on cyclic electron tunneling between a system with discrete energy levels and a single electron reservoir. When driven at a finite …
Controlled atomic scale fabrication of functional devices is one of the holy grails of nanotechnology. The most promising class of techniques that enable deterministic nanodevice fabrication are based on scanning probe patterning or surface assembly. However, this typically involves a complex process flow, stringent requirements for an ultra high vacuum environment, long fabrication times and, consequently, limited throughput and device yield. Here, a device platform is developed that overcomes these limitations by integrating scanning probe based dopant device fabrication with a CMOS-compatib…
After more than 30 years of validation of Moore's law, the CMOS technology has already entered the nanoscale (sub-100nm) regime and faces strong limitations. The nanowire transistor is one candidate which has the potential to overcome the problems caused by short channel effects in SOI MOSFETs and has gained signifi - cant attention from both device and circuit developers. In addition to the effective suppression of short channel effects due to the improved gate strength, the multi-gate NWFETs show excellent current drive and have the merit that they are compatible with conventional CMOS proce…
Ultralow p-type contact resistance for ultra-nanoscaled 2D-materials transistors
Singapore University of Technology and Design（新加坡科技设计大学）；China Jiliang University（中国计量大学）；Hubei Minzu University（湖北民族大学）；National University of Singapore（新加坡国立大学）
Spin-based logic devices could operate at very high speed with very low energy consumption and hold significant promise for quantum information processing and metrology. Here, an in-house developed, experimentally verified, ensemble self-consistent Monte Carlo device simulator with a Bloch equation model using a spin-orbit interaction Hamiltonian accounting for Dresselhaus and Rashba couplings is developed and applied to a spin field effect transistor (spinFET) operating under externally applied voltages on a gate and a drain. In particular, we simulate electron spin transport in a \SI{25}{nm}…
We report scanning tunneling microscopy studies of individual adatoms deposited on an InSb(110) surface. The adatoms can be reproducibly dropped off from the STM tip by voltage pulses, and impact tunneling into the surface by up to ~100x. The spatial extent and magnitude of the tunneling effect are widely tunable by imaging conditions such as bias voltage, set current and photoillumination. We attribute the effect to occupation of a (+/0) charge transition level, and switching of the associated adatom-induced band bending. The effect in STM topographic images is well reproduced by transport mo…
Mechanical strain plays a key role in the physics and operation of nanoscale semiconductor systems, including quantum dots and single-dopant devices. Here we describe the design of a nanoelectronic device where a single nuclear spin is coherently controlled via nuclear acoustic resonance (NAR) through the local application of dynamical strain. The strain drives spin transitions by modulating the nuclear quadrupole interaction. We adopt an AlN piezoelectric actuator compatible with standard silicon metal-oxide-semiconductor processing, and optimize the device layout to maximize the NAR drive. W…
