Transport in split gate MOS quantum dot structures (original) (raw)

Atomic-Scale, All Epitaxial In-Plane Gated Donor Quantum Dot in Silicon

Nano Letters, 2009

Nanoscale control of doping profiles in semiconductor devices is becoming of critical importance as channel length and pitch in metal oxide semiconductor field effect transistors (MOSFETs) continue to shrink toward a few nanometers. 1,2 Scanning tunneling microscope (STM) directed self-assembly of dopants is currently the only proven method for fabricating atomically precise electronic devices in silicon. To date this technology has realized individual components of a complete device with a major obstacle being the ability to electrically gate devices. Here we demonstrate a fully functional multiterminal quantum dot device with integrated donor based in-plane gates epitaxially assembled on a single atomic plane of a silicon (001) surface. We show that such in-plane regions of highly doped silicon can be used to gate nanostructures resulting in highly stable Coulomb blockade (CB) oscillations in a donor-based quantum dot. In particular, we compare the use of these all epitaxial in-plane gates with conventional surface gates and find superior stability of the former. These results show that in the absence of the randomizing influences of interface and surface defects the electronic stability of dots in silicon can be comparable or better than that of quantum dots defined in other material systems. We anticipate our experiments will open the door for controlled scaling of silicon devices toward the single donor limit.

Transition from MOSFET to Quantum Dot: An Overview

The quantization of electron energies in nano crystals leads to dramatic changes in electron transport and optical properties. For quantum effect to work properly in any system the spacing of energy level must be larger in comparison to K B T and for room temperature operation; this implies that the diameter of the potential box must be at most a few nano-meters. In this work, we have given theoretical idea of a quantum dot starting from the electron transport in MOSFET. Then, we have shown that for quantum effect to work properly the size of the quantum dot should be in nano-scale using quantum mechanics.

Finite-element analysis of a silicon-based double quantum dot structure

Physical Review B, 2006

We present finite-element solutions of the Laplace equation for the silicon-based trench-isolated double quantum-dot and the capacitively-coupled single-electron transistor device architecture. This system is a candidate for charge and spin-based quantum computation in the solid state, as demonstrated by recent coherent-charge oscillation experiments. Our key findings demonstrate control of the electric potential and electric field in the vicinity of the double quantum-dot by the electric potential applied to the in-plane gates. This constitutes a useful theoretical analysis of the silicon-based architecture for quantum information processing applications.

Multilayered gated lateral quantum dot devices

Applied Physics Letters, 2000

We describe a detailed device fabrication technique for the formation of a lateral quantum dot using a multilayered gated design. In our versatile system, a quantum dot is electrostatically defined by a split gate and two overlaying finger gates which introduce entrance and exit barriers to the dot. Periodic and continuous conductance oscillations arising from Coulomb charging effects are clearly observed in the transport properties at low temperatures.

Electron transport through a single InAs quantum dot

Physical Review B

InAs islands were embedded in the channel of an n-doped GaAs/AlGaAs high electron mobility transistor structure and a 60ϫ100 nm 2 constriction was defined by lithography based on the atomic-force microscope and subsequent wet chemical etching. Compared to an unpatterned device a strong shift of the threshold voltage to higher gate voltages and well-defined peaks were observed at the onset of the conductance. The energetic position as well as the magnetic-field-induced shift of the peaks confirm that electron transport through the p shell of a single InAs quantum dot ͑QD͒ is observed. Our experimental data are in excellent agreement with calculations based on a simple parabolic quantum dot potential. A Coulomb blockade energy of Ϸ12 meV is determined for electrons in the first excited QD state.

Film-thickness-dependent conduction in ordered Si quantum dot arrays

Nanotechnology, 2012

In recent years, silicon nanostructures have been investigated extensively for their potential use in photonic and photovoltaic applications. So far, for silicon quantum dots embedded in SiO 2 , control over inter-dot distance and size has only been observed in multiple bilayer stacks of silicon-rich oxides and silicon dioxide. In this work, for the first time the fabrication of spatially well-ordered Si quantum dots (QDs) in SiO 2 is demonstrated, without using the multilayer approach. This ordered formation, confirmed with TEM micrographs, depends on the thickness of the initially deposited sub-stoichiometric silicon oxide film. Grazing incidence x-ray diffraction confirms the crystallinity of the 5 nm QDs while photoluminescence shows augmented bandgap values. Low-temperature current-voltage measurements demonstrate film thickness and order-dependent conduction mechanisms, showing the transition from temperature-dependent conduction in randomly placed dots to temperature-independent tunnelling for geometrically ordered nanocrystals. Contrary to expectations from dielectric materials, significant conduction and photocarrier generation have been observed in our Si QDs embedded in SiO 2 demonstrating the possibility of forming initial film-thickness-controlled conductive films. This conduction via the silicon quantum dots in thick single layers is a promising result for integration into photovoltaic devices.

Three‐state quantum dot gate field‐effect transistor in silicon‐on‐insulator

IET Circuits, Devices & Systems, 2015

This paper presents the observation of intermediate state in the quantum dot gate field-effect transistors (QDGFETs) in silicon-on-insulator (SOI) substrate. Silicon dioxide (SiO 2)-cladded silicon (Si) quantum dots (QDs) are site-specifically selfassembled on the top of SiO 2 tunnel gate insulator on SOI substrates. Charge carrier tunnelling from the inversion channel to the QD layers on top of the gate insulator is responsible for the generation of intermediate state. Charge tunnelling is also verified by the C-V characteristics of the MOS device having same insulator structure as the gate region of the QDGFET. Considering the transfer of charge carriers from the inversion channel to two layers of SiO 2-cladded Si QDs, a model based on self-consistent solution of Schrödinger and Poisson equations, is also presented, to explain the generation of intermediate state.

Tunable few-electron double quantum dots with integrated charge read-out

Physica E-low-dimensional Systems & Nanostructures, 2004

We report on the realization of few-electron double quantum dots defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced to zero, while still allowing transport measurements through the double dot. The coupling between the two dots can be controlled even in the few-electron regime. Microwave radiation is used to pump an electron from one dot to the other by absorption of a single photon. The experiments demonstrate that this quantum dot circuit can serve as a good starting point for a scalable spin-qubit system.