A deep level transient spectroscopy (DLTS) study of defects created by low-fluence, low-energy ion implantation for development of ion-implanted silicon field-effect transistors for spin-dependent transport experiments is presented. Standard annealing strategies are considered to activate the implanted dopants and repair the implantation damage in test metal-oxide-semiconductor (MOS) capacitors. Fixed oxide charge, interface trapped charge and the role of minority carriers in DLTS are investigated. A furnace anneal at 950 $\rm ^{o}$C was found to activate the dopants but did not repair the implantation damage as efficiently as a 1000 $\rm ^{o}$C rapid thermal anneal. No evidence of bulk traps was observed after either of these anneals. The ion- implanted spin-dependent transport device is shown to have expected characteristics using the processing strategy determined in this study.
We have performed continuous wave and pulsed electron spin resonance measurements of implanted bismuth donors in isotopically enriched silicon-28. Donors are electrically activated via thermal annealing with minimal diffusion. Damage from bismuth ion implantation is repaired during thermal annealing as evidenced by narrow spin resonance linewidths (B_pp=12uT and long spin coherence times T_2=0.7ms, at temperature T=8K). The results qualify ion implanted bismuth as a promising candidate for spin qubit integration in silicon.
We present a technique to tune the charge density of epitaxial graphene via an electrostatic gate that is buried in the silicon carbide substrate. The result is a device in which graphene remains accessible for further manipulation or investigation. Via nitrogen or phosphor implantation into a silicon carbide wafer and subsequent graphene growth, devices can routinely be fabricated using standard semiconductor technology. We have optimized samples for room temperature as well as for cryogenic temperature operation. Depending on implantation dose and temperature we operate in two gating regimes…
A two stream model of boron diffusion in silicon has been developed. The model is intended for simulation of transient enhanced diffusion including redistribution of ion-implanted boron during low temperature annealing. The following mechanisms of boron diffusion were proposed, namely: the mechanism of a long-range migration of nonequilibrium boron interstitials and the mechanism due to the formation, migration, and dissolution of the "impurity atom - silicon self-interstitial" pairs. Based on the model, simulation of the redistribution of boron implanted into silicon substrates for annealing …
Spin-dependent transport processes in thin near-surface doping regions created by low energy ion implantation of arsenic in silicon are detected by two methods, spin-dependent recombination (SDR) using microwave photoconductivity and electrically detected magnetic resonance (EDMR) monitoring the DC current through the sample. The high sensitivity of these techniques allows the observation of the magnetic resonance in particular of As in weak magnetic fields and at low resonance frequencies (40-1200 MHz), where high-field-forbidden transitions between the magnetic substates can be observed due …
Modeling of ion-implanted boron redistribution in silicon crystals during low-temperature annealing with a small thermal budget has been carried out. It was shown that formation of "tails"' in the low-concentration region of impurity profiles occurs due to the long-range migration of boron interstitials
Special point defects in semiconductors have been envisioned as suitable components for quantum-information technology. The identification of new deep centers in silicon that can be easily activated and controlled is a main target of the research in the field. Vacancy-related complexes are suitable to provide deep electronic levels but they are hard to control spatially. With the spirit of investigating solid state devices with intentional vacancy-related defects at controlled position, here we report on the functionalization of silicon vacancies by implanting Ge atoms through single-ion impla…
Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation…
It has been shown that during thermal treatments of silicon layers preamorphized by germanium implantation and then implanted with boron ions the transport of impurity atoms occurs right up to a temperature of 850^{\circ}C due to migration of the nonequilibrium boron interstitials.
Crystalline Silicon-on-Sapphire (SOS) films were implanted with boron (B$^+$) and phosphorous (P$^+$) ions. Different samples, prepared by varying the ion dose in the range $10^{14}$ to 5 x $10^{15}$ and ion energy in the range 150-350 keV, were investigated by the Raman spectroscopy, photoluminescence (PL) spectroscopy and glancing angle x-ray diffraction (GAXRD). The Raman results from dose dependent B$^+$ implanted samples show red-shifted and asymmetrically broadened Raman line-shape for B$^+$ dose greater than $10^{14}$ ions cm$^{-2}$. The asymmetry and red shift in the Raman line-shape i…
It has been shown that many of the phenomena related to the formation of "tails" in the low-concentration region of ion-implanted impurity distribution are due to the anomalous diffusion of nonequilibrium impurity interstitials. These phenomena include boron implantation in preamorphized silicon, a "hot" implantation of indium ions, annealing of ion-implanted layers et cetera. In particular, to verify this microscopic mechanism, a simulation of boron redistribution during low-temperature annealing of ion-implanted layers has been carried out under different conditions of transient enhanced dif…
This work reports an ESR study of low energy, low fluence phosphorus ion implantation into silicon in order to observe the activation of phosphorus donors placed in close proximity to the Si-SiO2 interface. Electrical measurements, which were used to estimate donor activation levels, reported high implant recoveries when using 14 keV phosphorus ions however, it was not possible to correlate the intensity of the hyperfine resonance signal with the electrical measurements in the presence of an SiO2 interface due to donor state ionisation (i.e. compensation effects). Comparative measurements made…
Basic SiC bipolar transistors have been studied in the past for their applications where high power or high temperature operation is required. However since the current gain in SiC bipolar transistors is very low and therefore, a large base drive is required in high current applications. Therefore, it is important to enhance the current gain of SiC bipolar transistors. Using two dimensional mixed mode device and circuit simulation, for the first time, we report a new Darlington transistor formed using two polytypes 3C-SiC and 4H-SiC having a very high current gain as a result of the heterojunc…
We determined the interface state density ($D_{\rm it}$) distributions in the vicinity of the conduction band edge in silicon carbide (SiC) metal-oxide-semiconductor (MOS) structures by reproducing the experimental current-voltage characteristics of MOS field effect transistors (MOSFETs) with numerical calculations. In the calculation, potential distributions and energy sub-bands in the inversion layer were calculated by solving Poisson and Schrödinger equations, respectively. We demonstrate that gate characteristics of the MOSFETs are well described by considering that the interface states ar…
The reported diffusion constants for hydrogen in silicon vary over six orders of magnitude. This spread in measured values is caused by the different concentrations of defects in the silicon that has been studied. Hydrogen diffusion is slowed down as it interacts with impurities. By changing the material properties such as the crystallinity, doping type and impurity concentrations, the diffusivity of hydrogen can be changed by several orders of magnitude. In this study the influence of the hydrogen concentration on the temperature dependence of the diffusion in high energy proton implanted sil…
Graphene/silicon heterostructures have attracted tremendous interest as a new platform for diverse electronic and photonic devices such as barristors, solar cells, optical modulators, and chemical sensors. The studies to date largely focus on junctions between graphene and lightly-doped silicon, where a Schottky barrier is believed to dominate the carrier transport process. Here we report a systematic investigation of carrier transport across the heterojunctions formed between graphene and highly-doped silicon. By varying the silicon doping level and the measurement temperature, we show that t…
Electron-beam (e-beam) lithography is commonly used in fabricating metal-oxide-silicon (MOS) quantum devices but creates defects at the Si/SiO$_2$ interface. Here we show that a forming gas anneal is effective at removing shallow defects ($\leq$ 4 meV below the conduction band edge) created by an e-beam exposure by measuring the density of shallow electron traps in two sets of high-mobility MOS field-effect transistors (MOSFETs). One set was irradiated with an electron-beam (10 keV, 40 $μ$C/cm$^2$) and was subsequently annealed in forming gas while the other set remained unexposed. Low tempera…
Three types of first generation epitaxial graphene field effect transistors (FET) are presented and their relative merits are discussed. Graphene is epitaxially grown on both the carbon and silicon faces of hexagonal silicon carbide and patterned with electron beam lithography. The channels have a Hall bar geometry to facilitate magnetoresistance measurements. FETs patterned on the Si-face exhibit off-to-on channel resistance ratios that exceed 30. C-face FETs have lower off-to-on resistance ratios, but their mobilities (up to 5000 cm2/Vs) are much larger than that for Si-face transistors. Ini…
The photoluminescence and spin properties of ensembles of color centers in silicon carbide are enhanced by fabricating optically isolated slab waveguide structures and carefully controlling annealing and cooling conditions. We find that the photoluminescence signal of an ensemble of implanted defects is enhanced in slab waveguides by an order of magnitude over identically implanted bulk defects. The slab waveguide-enhanced photoluminescence of several defect species is used to study recombination and diffusion in the presence of thermal annealing with both rapid quench cooling and a longer ret…
A model of the interstitial diffusion of ion-implanted boron during rapid thermal annealing of silicon layers previously amorphized by implantation of germanium has been proposed. It is supposed that the boron interstitials are generated continuously during annealing due to dissolution or rearrangement of the clusters of impurity atoms which are formed in the ion-implanted layers with impurity concentration above the solubility limit. The local elastic stresses arising due to the difference of boron atomic radius and atomic radius of silicon also contribute to the generation of boron interstit…
Bismuth donors ion-implanted in $^{28}$Si and $^\text{nat}$Si are studied using magnetic resonance spectroscopy based on spin dependent recombination. The hyperfine clock transition, at which the linewidth is significantly narrowed, is observed for the bismuth donors. The experimental results are modeled quantitatively by molecular orbital theory for a coupled pair consisting of a bismuth donor and a spin dependent recombination readout center, including the effect of hyperfine and Zeeman interactions.
In the present work, we have investigated the performances of p plus minus Al0.3Ga0.7Sb Pocket Implanted L shaped GaSb InAs staggered bandgap SG heterojunction vertical n channel tunnel field effect transistors TFETs of 4 nm thin channel structures with the gate lengths of 20 nm. In this L shaped nonlinear geometry the gate electric field and tunnel junction internal field are oriented in same direction. We have used a 3 D full band atomistic sp3d5s spin orbital coupled tight binding method based quantum mechanical simulator. We have investigated current voltage characteristics, ON current, OF…
Spins in the `semiconductor vacuum' of silicon-28 ($^{28}$Si) are suitable qubit candidates due to their long coherence times. An isotopically purified substrate of $^{28}$Si is required to limit the decoherence pathway caused by magnetic perturbations from surrounding $^{29}$Si nuclear spins (I=1/2), present in natural Si (nat Si) at an abundance of 4.67%. We isotopically enrich surface layers of nat Si by sputtering using high fluence $^{28}$Si$^-$ implantation. Phosphorus (P) donors implanted into one such $^{28}$Si layer with ~3000 ppm $^{29}$Si, produced by implanting 30 keV $^{28}$Si$^-$…
The effect of polarization rotation on the performance of metal oxide semiconductor field-effect transistors was investigated with a Landau-Ginzburg-Devonshire theory based model. In this analytical model, depolarization field, polarization rotations and the electrostatic properties of the doped silicon substrate are considered to illustrate the size effect of ferroelectric oxides and the stability of polarization in each direction. Based on this model, we demonstrate that MOSFET operation could be achieved by polarization reorientation with a low operating voltage, if the thickness of ferroel…
The total dose radiation and annealing responses of the back transistor of Silicon-On-Insulator (SOI) pMOSFETs have been studied by comparing with those of the back transistor of SOI nMOSFETs fabricated on the same wafer. The transistors were irradiated by 60Co γ-rays with various doses, and the front transistors are biased in a Float-State and Off-State, respectively, during irradiation. The total dose radiation responses of the back transistors are characterized by their threshold voltage shifts. The results show that the total dose radiation response of the back transistor of SOI pMOSFETs, …
We present a realisation of high bandwidth instrumentation at cryogenic temperatures and for dilution refrigerator operation that possesses advantages over methods using radio-frequency single electron transistor or transimpedance amplifiers. The ability for the low temperature electronics to carry out faster measurements than with room temperature electronics is investigated by the use of a phosphorous-doped single-electron transistor. A single-shot technique is successfully implemented and used to observe the real time decay of a quantum state. A discussion on various measurement strategies …
The practical damage of silicon bipolar devices subjected to mixed ionization and displacement irradiations is usually evaluated by the sum of separated ionization and displacement damages. However, recent experiments show clear difference between the practical and summed damages, indicating significant irradiation synergistic effects (ISEs). Understanding the behaviors and mechanisms of ISEs is essential to predict the practical damages. In this work, we first make a brief review on the state of the art, critically emphasizing on the difficulty encountered in previous models to understand the…
Practical device architectures are proposed here for the implementation of three-terminal heterojunction bipolar transistor solar cells (3T-HBTSCs). These photovoltaic devices, which have a potential efficiency similar to that of multijunction cells, exhibit reduced spectral sensitivity compared with monolithically and series-connected tandem solar cells. In addition, the simplified n-p-n (or p-n-p) structure does not require the use of tunnel junctions. In this framework, four architectures are proposed and discussed in this paper: 1) one in which the top cell is based on silicon and the bott…
We have measured the optically injected excess carrier lifetime in silicon using photoexcited muon spin spectroscopy. Positive muons implanted deep in a wafer can interact with the excess carriers and directly probe the bulk carrier lifetime whilst minimizing the effect from surface recombination. The method is based on the relaxation rate of muon spin asymmetry, which depends on the excess carrier concentration. The underlying microscopic mechanism has been understood by simulating the four-state muonium model in Si under illumination. We apply the technique to different injection levels and …
We experimentally demonstrate DC functionality of graphene-based hot electron transistors, which we call Graphene Base Transistors (GBT). The fabrication scheme is potentially compatible with silicon technology and can be carried out at the wafer scale with standard silicon technology. The state of the GBTs can be switched by a potential applied to the transistor base, which is made of graphene. Transfer characteristics of the GBTs show ON/OFF current ratios exceeding 50.000.
我们展示了一种基于并五苯-金纳米颗粒有源层的有机存储晶体管器件。通过氨基封端的自组装单层将金（Au）纳米颗粒固定在并五苯晶体管的栅极电介质（二氧化硅）上。在栅上施加写入和擦除脉冲时，获得了较大的阈值电压漂移（22 V）和~ 3E 4的开/关漏电流比。晶体管的空穴场效应迁移率在导通和关断状态下相似（小于因子2）。观察到电荷保留时间高达4500 s。记忆效应主要归因于Au纳米颗粒。
The scattering of conduction electrons off neutral donors depends sensitively on the relative orientation of their spin states. We present a theory of spin-dependent scattering in the two dimensional electron gas (2DEG) of field effect transistors. Our theory shows that the scattering mechanism is dominated by virtual transitions to negatively ionized donor levels. This effect translates into a source-drain current that always gets reduced when donor spins are at resonance with a strong microwave field. We propose a model for donor impurities interacting with conduction electrons in a silicon …
The total ionizing dose irradiation (TID) effects of partially depleted (PD) silicon-on-insulator (SOI)devices which fabricated with a commercial 0.2 um SOI process are investigated. Experimental results show an original phenomenon that the ON irradiation bias configuration is the worst-case bias for both front-gate and back-gate transistor. To understand the mechanism, a charge distribution model is proposed. We think that the performance degradation of the devices is due to the radiation induced positive charge trapped in the bottom corner of shallow trench isolation (STI) oxide. In addition…
Silicon nanowires (Si NW) are ideal candidates for solution processable field effect transistors (FETs). The interface between the nanowire channel and the gate dielectric plays a crucial role in the FET performance, and it can be responsible for unwanted effects such as hysteresis of the I-V characteristics due to threshold voltage shift when the gate voltage is applied. Using gate-voltage bias stress measurements we show that a large hysteresis of up to 40V in Si NW FETs with SiO2 dielectric is mainly due to the holes traps at the nanowire/SiO2 interface. An approach for reducing this hyster…
As the conventional silicon metal-oxide-semiconductor field-effect transistor (MOSFET) approaches its scaling limits; many novel device structures are being extensively explored. Among them, the silicon nanowire transistor (SNWT) has attracted broad attention. To understand device physics in depth and to assess the performance limits of SNWTs, simulation is becoming increasingly important. The objectives of this work are: 1) to theoretically explore the essential physics of SNWTs (e.g., electrostatics, transport and band structure) by performing computer-based simulations, and 2) to assess the…
In this paper, we demonstrate by simulation the general usability of an electrostatically doped and electrically reconfigurable planar field-effect transistor (FET) structure. The device concept is partly based on our already published and fabricated silicon nanowire 3D-FET technology. The technological key features of this general purpose FET contain Schottky S/D junctions on a silicon-on-insulator (SOI) substrate additionally enabling high-temperature operation of the proposed device. The transistors charge carrier type, i.e. n- or ptype FET, is electrically switchable on the fly by applying…
The mechanism of the irradiation synergistic effect of Silicon bipolar junction transistors explained by multiscale simulations of Monte Carlo and excited-state first-principle calculations
Explosive crystallization (EC) is often observed when using nanosecond-pulsed melt laser annealing (MLA) in amorphous silicon (Si) and germanium (Ge). The solidification velocity in EC is so fast that a diffusion-less crystallization can be expected. In the contacts of advanced transistors, the active level at the metal/semiconductor Schottky interface must be very high to achieve a sub-10^{-9} ohm.cm2 contact resistivity, which has been already demonstrated by using the dopant surface segregation induced by MLA. However, the beneficial layer of a few nanometers at the surface may be easily co…
A 20 band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding (TB) model is used with a semi-classical, ballistic, field-effect-transistor (FET) model, to theoretically examine the bandstructure carrier velocity and ballistic current in silicon nanowire (NW) transistors. Infinitely long, uniform, cylindrical and rectangular NWs, of cross sectional diameters/sides ranging from 3nm to 12nm are considered. For a comprehensive analysis, n-type and p-type metal-oxide-semiconductor (NMOS and PMOS) NWs in [100], [110] and [111] transport orientations are examined. In general, physical…
The speed of silicon-based transistors has reached an impasse in the recent decade, primarily due to scaling techniques and the short-channel effect. Conversely, graphene (a revolutionary new material possessing an atomic thickness) has been shown to exhibit a promising value for electrical conductivity. Graphene would thus appear to alleviate some of the drawbacks associated with silicon-based transistors. It is for this reason why such a material is considered one of the most prominent candidates to replace silicon within nano-scale transistors. The major crux here, is that graphene is intri…
