P-type Silicon Substrates Research Articles

Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting

The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm−2 at −1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the native layer at cathodic potentials higher than −1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting.

Self-powered and temperature-tunable infrared-visible photodetector based on a VO2/Si heterojunction

In this work, a type-III heterojunction based on a pulsed-laser-deposited vanadium dioxide (VO2) and p-type silicon (p-Si) substrate is realized. The device shows a large self-powered and room-temperature photoresponse to IR (950 nm), green (515 nm) and blue (456 nm) LEDs. A short-circuit current (I sc) of ∼3 µA and an open-circuit voltage (V oc) of ∼−120 mV are observed under IR LED illumination. The work function data in literature along with the sign of V oc measurement is used to sketch the energy band diagram of the heterojunction. The temperature-dependent I sc properties of the junction, contrary to conventional photodetectors, show an initial rise and then a sharp transition from maximum (3.5 μA) to almost zero near 337 K, corresponding to a metal–insulator phase transition, paving the way for photodetectors with temperature-tunable photoresponsivity.

Multi-guard ring TCAD simulations for different n-on-p planar silicon particle detectors

This work presents a comparative study between three multi-guard ring structures that could be suitable for n-on-p silicon particle detectors for high luminosity applications. One multi-guard structure has p-type guard rings while the others have n-type guard rings with p-stop/p-spray isolation between n+ implants. The performance of the unirradiated structures are studied by increasing the fixed oxide charge density from 5 × 10+10 to 1 × 10+12 cm−2. It's found that for two structures there is a value of oxide charge density for which the breakdown voltage is maximum while for the third structure the breakdown voltage increases with oxide charge density. The performance of the irradiated structures are evaluated with simulations up to a radiation fluence of 1 × 10+16 1 MeV neutron equivalent/cm2/year (neq/cm2) using a three trap bulk radiation model for p-type silicon substrate. Structure with n-type guard rings and p-stop isolation exhibits low leakage current and good isolation between implants while structure with p-type guard rings shows higher breakdown voltage. The breakdown voltage is enhanced by adding floating metal field plates. TCAD simulation has been used to simulate current-voltage characteristics, electron and hole concentration profiles, and electric field and potential distributions.

Investigation of thermal annealing effects on MoO3 thin film by atomic layer deposition

Molybdenum oxide (MoO3) thin films have been obtained by plasma-enhanced atomic layer deposition using precursors of Mo(CO)6 and O2 plasma at a reactor temperature of 160 °C. The MoO3 thin films deposited on p-type silicon substrates with thermally grown 300 nm thick SiO2 layer with different numbers of ALD growth cycles. Spectroscopic ellipsometer is used to characterize as-grown film thickness and refractive index. The as-grown films are treated at annealing temperatures at 300–600 °C. The structural properties of as-grown and annealed thin films have been characterized by optical microscopy, µRaman spectra, and atomic force microscopy.

Fabrication of Zinc Oxide Nanoparticles Deposited on (3-Aminopropyl) Triethoxysilane-Treated Silicon Substrates by an Optimized Voltage-Controlled Electrophoretic Deposition and Their Application as Fluorescence-Based Sensors

In this study, a voltage controlled, reproducible, scalable, and cost-effective approach for depositing zinc oxide (ZnO) nanoparticles (NPs), using electrophoretic deposition (EPD) onto p-type silicon (Si) substrates, has been researched and analyzed for its feasibility with respect to electronic device fabrication and fluorescence-based sensors. Our work presents a detailed investigation to evaluate the influence of ZnO morphology, ZnO concentration, and the method of surface treatment applied to the underlying Si substrates, because these pertain to an optimized EPD system. It has been noted that the ZnO NP structures formed directly atop the (3-aminopropyl) triethoxysilane (APTES)-treated Si substrates were more adhesive, thus resulting in a higher yield of NPs over that of comparable depositions on bare silicon. Our observation is that smaller particle sizes of ZnO will increase the energy emission for fluorescence transmission, eliminate several peak emissions, obtain higher fluorescence quantum yield (FQY) efficiency, and require less excitation energy. The results obtained are promising in relation to the integration of EPD in the fabrication of nano biosensors, PV solar cells, nano electronic devices, and thin film transistors (TFTs), where ZnO improves the reliability, affordability, and increased sensitivity needed for the next generation of nanoscale devices and systems.

An Interface-Induced Dielectric Properties Degradation in Heterogeneous Stacked Device With P(VDF-TrFE)-Based Ferroelectric Polymers

Heterogeneous stacked electronics are one of the major topics in flexible electronics applications, which require high performances. At the same time, P(VDF-TrFE)-based polymers with unique characteristics, e.g., ferroelectric and flexible properties, also bring attention to heterogeneous stacked device applications. Since the interfacial characteristic has strong effects with performance and reliability, therefore, it becomes one of the key issues in P(VDF-TrFE)-based heterogeneous stacked devices. In this article, a mechanism of an interface trap charge-induced low-k interfacial layer was proposed and examined by experimental methods. To analyze the low-k interfacial layer effects, both general-doping (few 1015 cm−3) p-type and n-type silicon substrate were used. These experimental results showed that different types of silicon substrates have distinct interface properties. Then, different interface trap density ( $1.75\times 10^{12}$ – $4.1\times 10^{11}$ eV−1 cm−2) silicon substrates were fabricated to further analyze the low-k interfacial layer. These showed the substrate with the lowest interface trap density has less low-k interfacial effect than other substrates do. Based on these experimental verifications, the mechanism of interface trap charge-induced low-k interface characteristic was proposed. As a consequence, this interface trap–charge-induced behavior is a necessary consideration for applications of heterogeneous stacked devices.

Direct and alternating electrical performance of TiO2/SiO2/p-Si heterojunction under visible illumination

The titanium dioxide (TiO2) thin film was deposited on the surface of p-type silicon (Si) substrate using spray pyrolysis technique and TiO2/SiO2/p-Si heterojunction was formed. The microstructure of the heterojunction surface is characterized by X-ray diffraction and atomic force microscopy. The energy-band gap (~3.38 eV) and the work function (~5.53 eV) of the TiO2 thin film were calculated by ultraviolet-visible spectrum and ultraviolet photoelectron spectroscopy, respectively. The energy-band structure of the heterojunction is established. The current-voltage characteristics of the heterojunction is investigated, which displays a typical diode rectifying property. The alternating current capacitance and impedance are measured under different visible light intensities, and the heterojunction exhibits good photosensing performance. The resistance and impedance of the heterojunction decrease with increasing of light intensity, while the capacitance value increases. The phenomenon is mainly attributed to the decrease of Fermi level difference between TiO2 thin film and Si with the increase of light intensities, which can be explained by the energy-band diagram of the TiO2/SiO2/Si heterojunction.

On the Influence of Hydrocarbon Precursors and Elemental Composition on the Dielectric Properties and Conduction Mechanism of Hydrogenated Silicon Carbonitride Thin Films

Ternary compound thin films have drawn interest since intermediate forms can be developed for materials with tunable properties. Among them, thin films of silicon carbonitride (SiCN) are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another area of application of SiCN thin films is as low dielectric constant materials, which are desired for replacing silicon oxide (SiO2) or silicon nitride (Si3N4) in integrated circuits (IC) and charge trapping capacitors. In general, SiCN is an intermediate compound between Si3N4 which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with high mechanical durability [1].One of the most common techniques for the fabrication of SiCN thin films is plasma enhanced chemical vapour deposition (PECVD) with alkylsilazane precursors for high composition control [2]. Recently, we reported the compositional and mechanical properties of SiCN:H thin films, which were deposited using electron cyclotron resonance (ECR) PECVD with two different hydrocarbon precursors, acetylene (C2H2) and methane (CH4) [3, 4]. In the present work, we explore how film composition affects the electrical behaviour of the thin films. More specifically, we investigate the dielectric properties of SiCN:H thin films and the charge transportation and trapping mechanisms for different stoichiometries and film densities, as a function of the hydrocarbon precursor.Metal-insulator-semiconductor (MIS) capacitor type structures were formed on p-type (100) silicon substrates. Following the deposition, aluminum (Al) gate electrodes were sputtered for current-voltage (I-V) and capacitance-voltage (C-V) measurements operated at 1 MHz. The results were correlated with composition and density of SiCN:H thin films obtained from Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD), and variable angle spectroscopic ellipsometry (VASE) measurements. Finally, finite element modeling was performed by COMSOL to compare the capacitance characteristics in MIS structures of the thin films.[1] L.C Chen, C.K. Chen, S.L Wei, D.M Bhusari, K.H. Chen, Y.F. Chen, Y.C. Jong and Y.S. Huang. Crystalline silicon carbon nitride: A wide band gap semiconductor. Applied Physics Letters, 72(19), pp.2463-2465 (1998).[2] S. Bulou, L. Le Brizoual, P. Miska, L. de Poucques, R. Hugon, M. Belmahi, J. Bougdira. The influence of CH4 addition on composition, structure and optical characteristics of SiCN thin films deposited in a CH4/N2/Ar/hexamethyldisilazane microwave plasma. Thin Solid Films, 520(1), 245-250 (2011).[3] A. Abdelal, Z. Khatami and P. Mascher. Influence of Different Carbon Precursors on Optical and Electrical Properties of Silicon Carbonitride Thin Films. ECS Transactions, 97(2), 59 (2020).[4] Z. Khatami, G. B. F. Bosco, J. Wojcik, T. R. Tessler, P. Mascher. Influence of Deposition Conditions on the Characteristics of Luminescent Silicon Carbonitride Thin Films. ECS Journal of Solid-State Science and Technology, 7(2), N7 (2018).

Optical characterization of Ba0.5Sr0.5TiO3 material grown on a p-type silicon substrate (111) doped niobium oxide and chlorophyll

Barium Strontium Titanate (BST) is a material that has a dielectric constant and high load storage capacity. BST is made with 3 variations namely BST without container, BST in Niobium Oxide container, and BST in chlorophyll container. Percentage of container mass is 5% and 10% of BST mass. The method used is Chemical Solution Deposition (CSD). The process of growing thin films is done using Spin Coating with a speed of 3000 rpm for 30 seconds. The dropping process is carried out 3 times. The BST was turned at 850 °C for 22 hours of detention. The XRD characterization results showed that there was no structural shift from the BST that was made, this was seen from the lattice parameter values ​​obtained, namely 4.07Ǻ for BST, 4.07Ǻ for BST at 5% niobium oxide, 4.07Ǻ for BST at 10% niobium oxide, 4.06 Ǻ BST was taken by 5% chlorophyll, and 4.08 ST BST was taken by 10% chlorophyll. Characterization of optical properties showed that the addition of niobium oxide and chlorophyll reservoirs caused the absorbance of BST to decrease, the refractive index value to increase, and the gap energy value to decrease. Gap energy value is 2.23 eV at BST at 5% niobium oxide, 2.05 eV at BST at 10% niobium oxide, 2.46 eV at BST at 5% chlorophyll, and 2.47 eV at BST at 10% chlorophyll, where the energy gap value is based on literature 3.45 eV.

Effect of Co doping on optical parameters of SnO2 thin films

Abstract SnO2 thin films are deposited using spray pyrolysis technique on p-type silicon (Si) substrate by varying the Cobalt (Co) doping ratio from 3 to 5 at % in order to investigate the effect of the doping on the optical parameters of these films. Optical reflectance measurements are performed both for films and substrate. A simple analysis which is created as a combination of three different methods proposed earlier including the effect of the substrate is applied for the optical characterization of Co-doped SnO2 thin films. In addition to thickness, optical parameters such as refraction index and extinction coefficients are also obtained accurately, by applying this created procedure. The optical band gap and Urbach energy of the films are determined from the spectral dependence of the absorption coefficient. The refraction index and band gap energy of SnO2 films are found to be decreasing whereas Urbach energy is found to be increasing with increasing Co doping ratio. The roughness value of Co-doped SnO2 thin films on p-type Si is obtained with such a high precise only from reflectance spectrum.

Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications

The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.

Ion Species Dependence on the Interfacial Properties of Silicon Homojunctions Bonded Using an Ion Bombardment Treatment

Surfaces of (001) p-type silicon substrates were bombarded with either Ar or Kr ions prior to direct wafer bonding using an EVG© ComBond© high-vacuum wafer-bonding system.1 Previously, we showed that this ion bombardment treatment induces a thin ~nm amorphous region at the bonded interface.2 In this study, we extend upon this previous effort towards a fundamental understanding of this amorphous interfacial region by examining the dependence of the bonded interface’s properties with two different ion species. The ion energies used spanned from a factor of 0.5 to 2.5 times of a baseline energy E0. X-ray reflectivity measurements were performed on single unbonded wafers that were ion bombarded with either Ar or Kr to determine the thickness of the amorphous region as well as its mass density compared to bulk Si. Wafers treated with Ar showed no surface mass density dependence with ion energy, while wafers treated with Kr did show an ion energy dependence. While the Ar treatment reduces the surface density to ~80% of bulk Si density regardless of the energy used, the Kr treatment reduces the surface density to as low as ~70% of bulk Si density at 2.5⋅E0. Furthermore, for a given energy, the Ar treatment resulted in thicker layers than the Kr treatments, which is consistent with SRIM3 simulations because Kr is a heavier species than Ar. Current-voltage measurements were also used to probe the electrical properties of the bonded interfaces. Band structure modeling of the current-voltage measurements revealed that the amorphous region can be modeled with a step barrier that spans the thickness of the amorphous region.References Flötgen, et al., ECS Trans., 64(5), 103 (2014).E. Liao, et al., ECS Trans., 86(5), 55 (2018).F. Ziegler, et al., The Stopping Range of Ions in Solids vol. 1, (1985). Figure 1

Photo assisted negative differential resistance in porous silicon: A potential nano-structure for hot carrier solar cell

Abstract A device, supporting negative differential resistance, has been fabricated. Aluminum top contacts have been deposited on electrochemically synthesized porous silicon layer on p-type silicon substrate for this purpose. Top-bottom DC current vs. voltage (I-V) characteristics of the fabricated device have been recorded at room temperature under dark condition and injecting photons. Dark I-V characteristics of this device indicate the presence of negative differential resistance (NDR). Similar kind of I-V characteristics has been observed under illumination. At the same time, fabricated device shows photovoltaic effect after injecting photons. This may be due to some series and parallel combination of multiple junctions with photovoltaic nature.

Morphological, Structural, and Optical Properties of Silicon Nanostructures Formed in a Solution Containing Hydrogen Hexafluorosilicate H2(SiF6)

Photoluminescent boron-doped (100)-oriented porous silicon fabricated on a p-type silicon substrate by electrochemical etching in a solution containing fluorosilicic acid and ethanol is studied. The morphological, structural, and optical properties of silicon nanostructures obtained in solutions containing H2(SiF6) and ethanol are analyzed in comparison with the corresponding characteristics of samples formed in solutions of HF and ethanol. The morphological, structural, and optical properties were studied using scanning probe microscopy and spectrophotometry. It is shown that the porous silicon samples formed in solutions containing H2(SiF6) and ethanol have better optical properties, in particular, they exhibit more intense photoluminescence than the samples obtained in HF–ethanol solutions.

Room temperature high hydrogen gas response in Pd/TiO 2 /Si/Al capacitive sensor

This Letter reports the high gas response for hydrogen gas (H2) in Pd/TiO2/Si/Al based metal-oxide semiconductor (MOS) sensor. Titanium oxide (TiO2) thin film deposited on the p-type silicon (Si) substrate is used as the gate oxide of the MOS sensor. The surface morphology of thermally evaporated TiO2 thin film is investigated for the film structure using atomic force microscopy and scanning electron microscopy. The proposed MOS sensor characterised by capacitance–voltage (C–V) and conductance–voltage (G–V) measurements under exposure of different concentration of H2 gas at room temperature in the ambient-air atmosphere. The maximum gas response of 65% calculated from the change in capacitance and 84% calculated from the change in conductance are obtained for the exposure of 4% of H2 gas. The obtained maximum gas responses are highly promising for low concentration detection of hydrogen gas (4%) using the fabricated MOS sensor operated at room temperature under zero bias voltage condition.

Effects of deposition and annealing conditions on the crystallisation of NiTi thin films by e‐beam evaporation

This Letter demonstrates the effects of deposition and annealing conditions on the crystallisation of nickel–titanium (NiTi) thin films deposited by the e-beam evaporation. NiTi thin films of 0.5 μm thick are fabricated on P-type (110) silicon substrates using the e-beam evaporation technique. With the characterisations using the X-ray diffraction method, the results indicate that low e-beam deposition rate and argon employed annealing procedures can be beneficial to the formation of NiTi crystalline structure. Additionally, the as-deposited NiTi thin films without annealing procedures are amorphous, when deposited on the substrates at low temperatures. The differential scanning calorimetry studies show NiTi thin films formed by the e-beam evaporation are Ni-rich. Furthermore, SEM images illustrate that high-precision patterned NiTi thin film microstructures can be fabricated by combining with the e-beam evaporation and lift-off resist methods, without any wet or dry etching procedures. The proposed fabrication process for NiTi thin film microstructures shows great potential for application in shape memory alloy medical devices, as well as the micro-robotics.

Optical Characterization of GaN-Based Vertical Blue Light-Emitting Diodes on P-Type Silicon Substrate

Fabricating GaN-based light-emitting diodes (LEDs) on a silicon (Si) substrate, which is compatible with the widely employed complementary metal–oxide–semiconductor (CMOS) circuits, is extremely important for next-generation high-performance electroluminescence devices. We conducted a systematic investigation of the optical properties of vertical LEDs, to reveal the impacts of the manufacturing process on their optical characteristics. Here, we fabricated and characterized high-efficiency GaN-based LEDs with integrated surface textures including micro-scale periodic hemispherical dimples and nano-scale random hexagonal pyramids on a 4 inch p-type Si substrate. The highly reflective Ag/TiW metallization scheme was performed to decrease downward-absorbing light. We demonstrated the influence of transferring LED epilayers from a sapphire substrate onto the Si substrate on the emission characteristics of the vertical LEDs. The removal of the sapphire substrate reduced the adverse impacts of the quantum-confined Stark effect (QCSE). The influence of integrated surface textures on the light extraction efficiency (LEE) of the vertical LEDs was studied. With the injection current of 350 mA, vertical LEDs with integrated surface textures demonstrated an excellent light output power of 468.9 mW with an emission peak wavelength of 456 nm. This work contributes to the integration of GaN-based vertical LEDs into Si-based integrated circuits.

Enhanced open-circuit voltage in p-type passivated emitter and rear cell by doped polysilicon layer as passivation contact

The most promising and feasible approach to achieving high-efficiency silicon solar cells must be passivation contact compatible with current homojunction thermal processes. In this paper, an easy-to-implement carrier-selective passivation contact with doped poly-Si/SiOx for produing p-type passivated emitter and rear cell (PERC) was proposed. The passivation contact structure consisted of an ultra-thin SiOx layer capped with an intrinsic amorphous silicon (a-Si) layer prepared by low pressure chemical vapor deposition, which was deposited onto a p-type silicon substrate and then was doped and re-crystallized by a thermal phosphorus diffusion at 850 °C for 75 min. By optimizing the diffusion profile and cleaning time, a low dark recombination current density J0 ≈ 3 fA/cm2 and large minority carrier lifetime of 3000 μs were achieved on the 180-μm-thick n-type wafers with a resistivity of 3 Ω·cm, corresponding to an implied open-circuit voltage of 700 mV. P-type PERC cells with the highly doped poly-Si/SiOx passivated emitter demonstrated 683.97 mV of open-circuit voltage, showing more than 10 mV enhancement comparing with regular PERC cells. The results demonstrated an attractive potential of the carrier-selective passivation contacts with doped poly-Si/SiOx under front metallizatin area in photovoltaic application.

The Mole Fraction Effect on Magnetic Properties of Ba&lt;sub&gt;x&lt;/sub&gt;Sr&lt;sub&gt;1-x&lt;/sub&gt;TiO&lt;sub&gt;3 &lt;/sub&gt;(x = 0; 0.125; 0.25; 0.375; 0.500) Thin Film

Barium Strontium Titanate (BaxSr1-xTiO3) thin films have been synthesized for mole fraction = 0; 0.125; 0.25; 0.375; and 0.500 using Chemical Solution Deposition (CSD) method. The thin film was grown on p-type silicon (100) substrate using spin coating technique and annealed at 850∘C for 8 hours with an increasing rate of 1.67∘C/minute. The BST thin film was characterized using LCR meter to obtain data on frequency, charge, and electrical current. We also model the occurrence of vicinity magnetic induction around the thin film produced by the current flow in the BST thin film. The electrical and magnetic induction response of BST thin film with variation of mole fraction are presented here.

Room temperature gas sensor based on La2O3 doped CuO thin films

In this work, undoped and lanthanum doped cupric oxide (CuO:La) nanorods structured thin films were deposited at different concentrations (CLO) on p-type silicon substrates using the spray pyrolysis technique at 350 °C. XRD, AFM, SEM, and EDX techniques were used to investigate the structural, morphological, and compositional analysis, respectively. A decrease in crystallite size was observed from 13.4 to 7.75 nm and even the peak diffraction intensity decreased with an increase in La concentration. The hexagonal structure of the La2O3 phase with poor orientation planes was observed at 7 wt% La. Amplitude parameters, grain size, and atoms distribution were discussed from AFM analysis. SEM images show a uniform distribution and homogeneous crystalline construction supported by quadrilateral pillars with nanorods-like in shape. The sensitivity, recovery, and response time for CLO thin films as room temperature NO2 sensor devices were calculated. The effect of lanthanum concentration on the sensing mechanism of CuO thin films also has been reported.