Silicon Doping Concentration Research Articles

The potential of heavily doped n-type silicon in plasmonic sensors

In this paper, we introduce a CMOS-compatible H-shaped plasmonic sensor with a silicon-insulator-silicon (SIS) configuration, utilizing highly doped n-type silicon as an alternative to traditional plasmonic materials like silver and gold. By employing precise carrier concentrations, we tune both the real and imaginary parts of permittivity, enabling the negative real permittivity required for efficient surface plasmon polariton (SPP) propagation. Our findings reveal a significant correlation between silicon doping concentration and sensitivity, highlighting the optimization potential of n-type silicon for advanced plasmonic applications. Through Finite Element Method (FEM) optimization, the sensor achieved a peak sensitivity of 5841.43 nm/RIU and a FOM of 23.8426. The sensor’s capabilities extend to temperature sensing with PDMS and ethanol, blood electrolyte detection for sodium and potassium, chemical detection, and magnetic field sensing. By utilizing minute changes in resonant wavelength through SPPs and SIS structures, our approach underscores n-type silicon’s potential in advancing plasmonic sensor technology.

Photometry, Centroid and Point-spread Function Measurements in the LSST Camera Focal Plane Using Artificial Stars

The Vera C. Rubin Observatory’s LSST Camera (LSSTCam) pixel response has been characterized using laboratory measurements with a grid of artificial stars. We quantify the contributions to photometry, centroid, point-spread function size, and shape measurement errors due to small anomalies in the LSSTCam CCDs. The main sources of those anomalies are quantum efficiency variations and pixel area variations induced by the amplifier segmentation boundaries and “tree-rings”—circular variations in silicon doping concentration. This laboratory study using artificial stars projected on the sensors shows overall small effects. The residual effects on point-spread function (PSF) size and shape are below 0.1%, meeting the ten-year LSST survey science requirements. However, the CCD mid-line presents distortions that can have a moderate impact on PSF measurements. This feature can be avoided by masking the affected regions. Effects of tree-rings are observed on centroids and PSFs of the artificial stars and the nature of the effect is confirmed by a study of the flat-field response. Nevertheless, further studies of the full-focal plane with stellar data should more completely probe variations and might reveal new features, e.g., wavelength-dependent effects. The results of this study can be used as a guide for the on-sky operation of LSSTCam.

Silicon-doped β-Ga2O3 films grown at 1 µm/h by suboxide molecular-beam epitaxy

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 µm/h with control of the silicon doping concentration from 5 × 1016 to 1019 cm−3. In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 µm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 µm thick films). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the β-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 µm thick film with a mobile carrier concentration of 2.7 × 1017 cm−3 reveal a room-temperature mobility of 124 cm2 V−1 s−1 that increases to 627 cm2 V−1 s−1 at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal–semiconductor field-effect transistors made from these silicon-doped β-Ga2O3 films grown by S-MBE at growth rates of ∼1 µm/h.

Understanding of temperature-dependent photoluminescence in graphite and SixZnO(1-x) tri-composite nanostructure

The thermal transport behaviour of any material can be studied using electron trapping over its defects levels at varying temperatures. In this article, we describe temperature-dependent photoluminescence of tri-composite nanostructures formed using graphite, Si and ZnO [Graphite:SixZnO(1-x)]. The absorption spectra and Tauc's relationship measures the band gap of Graphite:SixZnO(1-x) tri-composite nanostructures which are obtained for all the value of 'x' keeping the concentration of graphite constant. It is observed that due to the presence of Si and ZnO, the band gap of the combined nanostructure of Graphite:SixZnO(1-x) gets widened. The outcomes of XRD/EDX reveal the presence of graphite, Si and ZnO in the obtained tri-composite nanostructure. The clear formation of nanostructures ranges (200–500) nm has been investigated and is found to be consistent with the XRD/EDX findings. Our results suggest that at elevated temperature electron gets trapped over defects levels which can be measured using photoluminescence intensity. This information provides an insight mechanism for the excitation of electrons from the conduction band to the valence band of Graphite:SixZnO(1-x) tri-composite nanostructures. However, the number of defects level and doping concentration both are linked with photoluminescence intensity. Therefore a trade-off is made between electron trapping over the defects levels at elevated temperature and on higher silicon doping concentration in Graphite:SixZnO(1-x). This trade-off is well explained using increment/decrement in photoluminescence intensity and with the excitation of the electron with a suitable band diagram. Finally, the possible device applications employing the fabricated Graphite:SixZnO(1-x) tricomposite nanostructures has also been explored using the Commission International de I'Eclairage (CIE) diagram and is found to be in efficient designing of future light emitting diodes (LEDs).

Graphene-silicon-graphene Schottky junction photodetector with field effect structure.

Graphene has unique advantages in ultrabroadband detection. However, nowadays graphene-based photodetectors cannot meet the requirements for practical applications due to their poor performance. Here, we report a graphene-silicon-graphene Schottky junction photodetector assisted by field effect. Two separate graphene sheets are located on both sides of the n-doped silicon to form two opposite lateral series heterojunctions with silicon, and a transparent top gate is designed to modulate the Schottky barrier. Low doping concentration of silicon and negative gate bias can significantly raise the barrier height. Under the combined action of these two measures, the barrier height increases from 0.39 eV to 0.77 eV. Accordingly, the performance of the photodetector has been greatly improved. The photoresponsivity of the optimized device is 2.6 A/W at 792 nm, 1.8 A/W at 1064 nm, and 0.42 A/W at 1550 nm, and the on/off photo-switching ratio reaches 104. Our work provides a feasible solution for the development of graphene-based optoelectronic devices.

Establishment and verification of resistance temperature coefficient model of P-type non-uniformly doped resistance

In this paper, a first-order average temperature coefficient of resistance () calculation model is established and analyzed based on the distribution of piezoresistive doping concentration in bulk silicon. Furthermore, by extracting the experimental results of the first-order of multiple research groups and combining the first-order calculation model, the new mobility model in the concentration range of piezoresistance (1 × 1018–1 × 1020 at cm−3) is obtained by fitting. The first-order of five implantation concentrations under the same process is tested. The results show that the error between the first-order obtained based on the new mobility calculation model and the test results is within 5%. However, the first-order based on the Arora mobility model has a deviation of 104.6% under the implantation condition of 3.75 × 1015 at cm−2. At the same time, the effects of different annealing temperatures and time on the first-order at the implantation concentration of 8.5 × 1013 at cm−2 are compared. The results show that a higher annealing temperature or longer annealing time is not conducive to reducing the first-order , but the difference is small.

Advances in tuning band gap of graphene by potential doping using DFT: a review

Graphene: a sp2 carbon system is a zero band gap semiconductor. In spite of having extraordinary properties, opening of band gap is the bottleneck in the path of graphene for becoming the heart of all modern electronics. Chemical doping can prove itself to be the fastest solution to this problem as it is one of the most informal approaches to induce band gap in pristine. Due to tiny nanostructures and dimensions of graphene, modelling and simulative study of graphene is more effective and confirmative than experimental results. In this study we have compared our results with the previous works, our simulation matches well with the previous works. The main concern is on the substitution and pair doping of BN, B and N open up an energy band gap up to (0.379eV) and (0.386eV). Codoping of B-N create a band gap up to (0.712eV) and pair doping shows that 1BN(0.616eV), 2BN(0.386eV), 3BN pair create a sharp increase in band gap up to (1.457eV) when substitute on graphene, while the substitution doping and increased in the super cell models with the same doping concentration of silicon induced a band gap of 1.019eV, where Si doping on different super cell shows a band gap enhancement from 0.57eV at (6x6) model to 1.90eV at (5x5) model and change its nature from semimetal to semiconductor. The present review article focuses on the alteration of electronic and optical properties by adding different dopants on to the graphene sheets, using density functional theory (DFT) calculations. Doping can improve the electronic properties of graphene by producing a small band gap in it, resulting in the appropriateness of this interesting material for modern electronics. Different codes and approximations have been applied to tune the band structure of graphene that has been discussed in the article.

Effect of silicon dopant on mechanical properties of monolayer graphene

The exceptional qualities of graphene have drawn the attention of many researchers and scientists. It has exhaustive real-life applications, ranging from mechanical and medical domain to electronic fields. The significant properties of graphene can be tailored by chemical functionalization methods. By incorporating foreign atoms, the properties of pristine graphene can be modified. Molecular dynamics (MD) simulations are carried out to conduct tensile tests on square-shaped graphene doped by silicon. The fracture strength, failure strain and Young’s modulus are measured on grapheme doped by silicon. The carbon atoms in the graphene sheet are replaced randomly with silicon atoms for this simulation and the variation of mechanical properties are observed by comparing with the pristine form of graphene. The properties such as Young’s modulus, fracture strength and failure strain are found to reduce with the increase of doping intensity. During chemical vapour deposition (CVD) method as silicon atoms are likely to replace the carbon atoms, it may promote the electronic properties but in the present study, it is found to decline its mechanical properties due to increase in silicon doping concentration. As a result, it is therefore suggested to consider the effect of silicon dopants in the applications of graphene.

Tree rings in Large Synoptic Survey Telescope production sensors: its dependence on radius, wavelength, and back bias voltage

Tree rings are one of the sensor effects that may affect precise measurements in the Large Synoptic Survey Telescope (LSST). The effect is caused by silicon wafer manufacturing process, resulting in formation of circular patterns due to variations of the silicon dopant concentration. We have analyzed flat-field images taken at Brookhaven National Laboratory and SLAC for all production sensors used to build the LSST camera in order to measure the amplitudes and periods of the tree ring patterns as a function of the radius, illumination wavelength, and sensor back bias voltage. With nominal back bias voltage settings, the tree ring amplitudes and periods for both ITL and e2v sensors are considered to have small impact on the galaxy shear measurement in LSST.

ToF-SIMS 3D Analysis of Thin Films Deposited in High Aspect Ratio Structures via Atomic Layer Deposition and Chemical Vapor Deposition.

For the analysis of thin films, with high aspect ratio (HAR) structures, time-of-flight secondary ion mass spectrometry (ToF-SIMS) overcomes several challenges in comparison to other frequently used techniques such as electron microscopy. The research presented herein focuses on two different kinds of HAR structures that represent different semiconductor technologies. In the first study, ToF-SIMS is used to illustrate cobalt seed layer corrosion by the copper electrolyte within the large through-silicon-vias (TSVs) before and after copper electroplating. However, due to the sample’s surface topography, ToF-SIMS analysis proved to be difficult due to the geometrical shadowing effects. Henceforth, in the second study, we introduce a new test platform to eliminate the difficulties with the HAR structures, and again, use ToF-SIMS for elemental analysis. We use data image slicing of 3D ToF-SIMS analysis combined with lateral HAR test chips (PillarHall™) to study the uniformity of silicon dopant concentration in atomic layer deposited (ALD) HfO2 thin films.

Analytical Models for the electric field and potential of AlGaN/GaN HEMT with partial silicon doping

Here, we study the mechanism of AlGaN/GaN HEMT with the partial silicon doping in the AlGaN layer under reverse bias and propose a two-dimensional analytic model for this device. The local density of two-dimensional electron gas (2DEG) increase at the interface between the AlGaN and GaN buffer due to partial silicon positive charge. And a new electric field peak is introduced by electric field modulation effect, which makes the electric field distribution of the channel surface more uniform and increases the breakdown voltage of the device. An analytical expression for the electric field and potential distribution of the channel is obtained, based on the two-dimensional Poisson's equation with appropriate boundary conditions. With this model, we explain the effects of silicon doping concentration and doping length on channel potential and electric field distribution in detail. By comparing the results obtained by the analytical model with the simulation results of Silvaco TCAD software, the numerical results and simulation results mostly match which verifies the validity of the model and provides a reference to model other AlGaN/GaN HEMTs.

Thermal transport characterization of carbon and silicon doped stanene nanoribbon: an equilibrium molecular dynamics study.

Equilibrium molecular dynamics simulation has been carried out for the thermal transport characterization of nanometer sized carbon and silicon doped stanene nanoribbon (STNR). The thermal conduction properties of doped stanene nanostructures are yet to be explored and hence in this study, we have investigated the impact of carbon and silicon doping concentrations as well as doping patterns namely single doping, double doping and edge doping on the thermal conductivity of nanometer sized zigzag STNR. The room temperature thermal conductivities of 15 nm × 4 nm doped zigzag STNR at 2% carbon and silicon doping concentration are computed to be 9.31 ± 0.33 W m−1 K−1 and 7.57 ± 0.48 W m−1 K−1, respectively whereas the thermal conductivity for the pristine STNR of the same dimension is calculated as 1.204 ± 0.21 W m−1 K−1. We find that the thermal conductivity of both carbon and silicon doped STNR increases with the increasing doping concentration for both carbon and silicon doping. The magnitude of increase in STNR thermal conductivity due to carbon doping has been found to be greater than that of silicon doping. Different doping patterns manifest different degrees of change in doped STNR thermal conductivity. Double doping pattern for both carbon and silicon doping induces the largest extent of enhancement in doped STNR thermal conductivity followed by single doping pattern and edge doping pattern respectively. The temperature and width dependence of doped STNR thermal conductivity has also been studied. For a particular doping concentration, the thermal conductivity of both carbon and silicon doped STNR shows a monotonic decaying trend at elevated temperatures while an opposite pattern is observed for width variation i.e. thermal conductivity increases with the increase in ribbon width. Such comprehensive study on doped stanene would encourage further investigation on the proper optimization of thermal transport characteristics of stanene nanostructures and provide deep insight in realizing the potential application of doped STNR in thermoelectric as well as thermal management of stanene based nanoelectronic devices.

Glass composites reinforced with silicon-doped carbon nanotubes

Glass composite reinforcement by addition of carbon nanotubes (CNTs) is limited due to generally poor load transfer between the matrix and “slippery” reinforcing element. Using computational methods, here we investigate how this load transfer challenge can be overcome by doping the CNT walls with silicon atoms, to create a novel high performance glass composite reinforced with such silicon-doped CNTs (Si-CNTs). It is shown, from first-principles density functional calculations, how silicon dopants in the CNTs should covalently bind with oxygen atoms from the SiO2-glass, resulting in strong interfacial bonding and effective load transfer between the CNTs and the matrix. Molecular dynamics (MD) simulations of this new Si-CNTs reinforced glass composite reveal both ∼10 times increase of the interfacial traction and up to 60% increase of the Young's modulus. A modified shear-lag model is derived, for predicting the composite's Young's modulus, for finite-length CNTs in matrices, as a function of the interfacial strength, the CNT aspect ratio, and the silicon-dopant concentration. The model can also be extended to other similar short-fiber composites.

Reconstructing photoluminescence spectra at liquid nitrogen temperature from heavily boron‐doped regions of crystalline silicon solar cells

AbstractWhen measured at low temperature (79 K), the photoluminescence (PL) spectra from silicon wafers containing a diffused heavily doped layer exhibit a second peak due to band gap narrowing in the diffused region. This work aims to decompose this peak into components arising from the various doping concentrations within the diffused layer. Whilst the peak position of silicon band‐to‐band PL spectra changes significantly with the doping concentration in silicon, the shape of the spectra also varies strongly with doping concentrations due to the broadening effects of band‐filling and band‐tail states. By measuring PL spectra on a range of uniformly heavily doped wafers, we show that these changes in spectral position and shape can be accurately modelled for doping concentrations above 1 × 1019 cm−3 using simple parameterisations, with minimal impact of variations in excitation intensity or injection level. This allows the PL spectra for a range of arbitrary doping concentrations to be reconstructed. We then show that the PL spectra from a thermally boron‐diffused wafer, in which the boron concentration changes with depth, can be reconstructed based on a superposition of PL spectra arising from the layers of different doping beneath the surface. Furthermore, the scaling factor for each layer can be accurately estimated based on the doping profile and the fraction of incident light absorbed in the layer.

Minimizing Isolate Catalyst Motion in Metal-Assisted Chemical Etching for Deep Trenching of Silicon Nanohole Array.

The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates. While the triggering events are stochastic, the doping concentration of silicon offers a good control in minimizing isolate catalyst motion. The doping concentration affects the porosity at the etching front, and this directly affects the van der Waals (vdWs) forces between the metal catalyst and Si during etching. A reduction in the vdWs forces resulted in a lower bending torque that can prevent the straying of the isolate catalyst from its directional etching, in the event of unequal etch rates. The key understandings in isolate catalyst motion derived from this work allowed us to demonstrate the fabrication of large area and uniformly ordered sub-500 nm nanoholes array with an unprecedented high aspect ratio of ∼12.

Silicon Luminescence Spectra Modelling and the Impact of Dopants

This paper presents findings on applying physical models in the literature to describe silicon luminescence spectra at 80 – 300K. Incorporation of exciton recombination models are shown to disagree with the measured luminescence spectra, whereas a free electron-hole recombination model is shown to match well with the luminescence spectra. However, the lack of consideration for excitons is not justified, as Bludau et al. [J. Appl. Phys., vol. 45, p. 1846, 1974] reported that excitons are present even at room temperature. The second part of the paper demonstrates the impact of shallow dopants on the silicon luminescence spectra at 79K. The ratio of the dopant-related peak to the band-to-band peak intensities correlates with the dopant concentration, indicating that luminescence spectroscopy has the potential for quantifying dopant concentrations in silicon in this temperature range.

Quantifying boron and phosphorous dopant concentrations in silicon from photoluminescence spectroscopy at 79 K

Photoluminescence spectroscopy at 79 K is shown to provide an alternative, non‐destructive characterisation method for quantifying the boron and phosphorous dopant concentrations in silicon. The dopant concentrations are revealed by the photoluminescence intensity ratios of the dopant‐related features to the band‐to‐band recombination peaks. The intensity ratio is found to be insensitive to the excitation power in a wide range of 0.3 W cm−2–100 kW cm−2. Calibration curves for boron and phosphorous in silicon are presented for [B] below 5 × 1017 cm−3 and [P] below 8 × 1016 cm−3.

Pulsed KrF excimer laser dopant activation in nanocrystal silicon in a silicon dioxide matrix

We demonstrate that a pulsed KrF excimer laser (λ = 248 nm, τ = 22 ns) can be used as a post-furnace annealing method to greatly increase the electrically active doping concentration in nanocrystal silicon (ncSi) embedded in SiO2. The application of a single laser pulse of 202 mJ/cm2 improves the electrically active doping concentration by more than one order of magnitude while also improving the conductivity. It is confirmed that there is no film ablation or significant change in ncSi structure by atomic force microscopy and micro-Raman spectroscopy. We propose that the increase in free-carrier concentration is the result of interstitial P/B dopant activation, which are initially inside the Si crystallites. Evidence of mobility limited carrier transport and degenerate doping in the ncSi are measured with temperature-dependent conductivity.

Influence of metallic catalyst and doping level on the metal assisted chemical etching of silicon

The presented work shows a study of the boundary condition between metal and silicon, in metal assisted chemical etching. This is achieved by varying silicon doping type and concentration as well as metal type and oxidation agent concentration. First, the etch rate dependence of silver particles, on n- and on p-doped samples is investigated revealing different etch rates depending on doping concentration. Additional experiments using an etch solution containing no oxidation agent show an impact of the metal–semiconductor combination on the etch process. In this case the higher work function of Pt particles compared to Ag leads to an etching independent of silicon doping.

Controlling the dopant dose in silicon by mixed-monolayer doping.

Molecular monolayer doping (MLD) presents an alternative to achieve doping of silicon in a nondestructive way and holds potential for realizing ultrashallow junctions and doping of nonplanar surfaces. Here, we report the mixing of dopant-containing alkenes with alkenes that lack this functionality at various ratios to control the dopant concentration in the resulting monolayer and concomitantly the dopant dose in the silicon substrate. The mixed monolayers were grafted onto hydrogen-terminated silicon using well-established hydrosilylation chemistry. Contact angle measurements, X-ray photon spectroscopy (XPS) on the boron-containing monolayers, and Auger electron spectroscopy on the phosphorus-containing monolayers show clear trends as a function of the dopant-containing alkene concentration. Dynamic secondary-ion mass spectroscopy (D-SIMS) and Van der Pauw resistance measurements on the in-diffused samples show an effective tuning of the doping concentration in silicon.