The Effects of Dopant Concentration on the Performances of the a-SiOx:H(p)/a-Si:H(i1)/a-Si:H(i2)/µc-Si:H(n) Heterojunction Solar Cell

In this work, the imbalances in band gap energy between p-window layer and intrinsic layer (p/i interface) in p-i-n type solar cells to suppress charge recombination adopting with the addition of buffer layer, at p/i interface, namely solar cell structures without buffer (Cell A) and with buffer (Cell B). Using well-practiced AFORS-HET software, performances of Cell A and Cell B structures are evaluated and compared to experimental data. A good agreement between AFORS-HET modelling and experimental data was obtained for Cell A (error = 1.02%) and Cell B (error = 0.07%), respectively. The effects of dopant concentrations of the p-type and n-type were examined with respect to cell B for better performance by analysing the energy band diagram, the electric field distribution, the trapped hole density, the light J-V characteristics, and the external quantum efficiency. The simulated results of an optimised Cell B showed that the highest efficiency of 8.81% (VOC = 1042 mV, JSC = 10.08 mA/cm2, FF = 83.85%) has been obtained for the optimum dopant values of NA = 1.0 x 1019 cm-3 and ND = 1.0 x 1019 cm-3, respectively. A comparison between experimental data and simulation results for Cell B showed that the conversion efficiency can be enhanced from 5.61% to 8.81%, using the optimized values

Tfet Biosensor Simulation and Analysis for Various Biomolecules

This paper investigates the simulation and performance of Tunnel field effect transistor (TFET) with a nanocavity in it, which can be used for bio sensing application. The entire simulation is done using the tool Silvaco Atlas TCAD. This paper mainly aims in comparing the different parameters for few biomolecules which has different dielectric constant values, namely Streptavidin, Biotin, APTES, Cellulose and DNA. The device structure here consists of a nanocavity near the source end, which is used to place these biomolecules and hence observe the variation of the Drain current v/s Gate voltage characteristic graph, these biomolecules that are having unique dielectric constants are placed within this cavity and these graphs are observed. The energy band diagram of this device is obtained; on top of this various other parameters namely Surface Potential, Electric field are observed for the above-mentioned Biomolecules. The Length of the cavity of the biosensor is also varied to observe the difference, in addition to this Ion (ON current) variation is plotted for the change in the dielectric constant of the biomolecule.

Overlapped Gate-Source/Drain H-shaped TFET: Proposal, Design and Linearity Analysis

In this paper, the proposed design of H-shaped TFET has been discussed. This design is providing a high Ion/Ioff ratio with better Ion. HfO2 is used for better tunneling current. With this device, Different parameters such as unit parameter, analogue parameter, and linearity parameter have been studied and investigated the output of the H-TFET. As unit parameters, the electric field, electric potential, energy band diagram, and non-local band-to-band tunneling rate (BTBT) have all been observed. Second and third-order harmonics distortion (HD2, HD3), third-order current intercept point (IIP3), third-order intermodulation distortions (IMD3), and second and third-order voltage intercept point (VIP2, VIP3) are evaluated as linearity parameters that characterize the device's distortions and linearity. We obtained Ion\({\text{=1.6×}10}^{-4}\) A/µm, Ioff=2.1\({\text{×}10}^{-19}\) A/µm, Ion /Ioff=7.6\({\text{×}10}^{14}\),threshold voltage Vt=0.3449 V. © 2017 Elsevier Inc. All rights reserved.

Demonstration of TiO2 Based Ultra High-k (k = 30) Metal-Insulator–Semiconductor Capacitor and Its Electrical Properties

In this paper, we investigated TiO2 as gate dielectric to achieve the large dielectric constant. The ultra high-k value over 30 was obtained by Capacitance–Voltage measurement of Al/Ti/TiO2/Si Metal-Insulator–Semiconductor (MIS) capacitor. Among as deposited, rapid thermal annealing (RTA) at 750 °C and 1000 °C, the RTA at 750 °C showed the lowest gate leakage current. It implies that TiO2 has optimum RTA temperature having the lowest leakage current. When TiO2 is annealed at 750 °C, the phase of TiO2 changes to anatase and interfacial layer between TiOx and Si was formed. While TiO2 is annealed at 1000 °C, the phase of TiO2 changes to rutile and diffusion of silicon atoms was clearly observed and it causes the silicide formation. Based on measurement data, we proposed the energy band diagram of Al/TiO2/Si MIS capacitors. This diagram shows that the energy band gap of RTA at 750 °C is expanded while that of RTA at 1000 °C is contracted. In addition, TiO2 with RTA at 550 °C was tested to confirm leakage current and it shows lower leakage current than RTA at 750 °C as we expected. This result confirmed that optimum RTA temperature of TiO2 would exist under 750 °C.

Reduced graphene oxide on silicon-based structure as novel broadband photodetector

Heterojunction photodetector based on reduced graphene oxide (rGO) has been realized using a spin coating technique. The electrical and optical characterization of bare GO and thermally reduced GO thin films deposited on glass substrate has been carried out. Ultraviolet–visible–infrared transmittance measurements of the GO and rGO thin films revealed broad absorption range, while the absorbance analysis evaluates rGO band gap of about 2.8 eV. The effect of GO reduction process on the photoresponse capability is reported. The current–voltage characteristics and the responsivity of rGO/n-Si based device have been investigated using laser diode wavelengths from UV up to IR spectral range. An energy band diagram of the heterojunction has been proposed to explain the current versus voltage characteristics. The device demonstrates a photoresponse at a broad spectral range with a maximum responsivity and detectivity of 0.20 A/W and 7 × 1010 cmHz/W, respectively. Notably, the obtained results indicate that the rGO based device can be useful for broadband radiation detection compatible with silicon device technology.

ZnO/RGO Heterojunction Based near Room Temperature Alcohol SENSOR with Improved Efficiency

The systematic optimization of surface engineering (dimensionality) indeed plays a crucial role in achieving efficient vapor-sensing performance. Among various semiconducting metal oxides, owing to some of its unique features and advantages, ZnO has attracted researchers on a global scale due to its application in various fields, including chemical sensors. The concomitant optimization of the surface attributes (varying different dimensions) of ZnO have become a sensation for the entire research community. Moreover, the small thickness and extremely large surface of exfoliated 2D nanosheets render the gas sensing material an ideal candidate for achieving strong coupling with different gas molecules. However, temperature is a crucial factor in the field of chemical sensing. Recently, graphene-based gas sensors have attracted attention due to their variety of structures, unique sensing performances and room temperature working conditions. In this work, a highly sensitive and fast responsive low temperature (60 °C)-based ethanol sensor, based on RGO/2D ZnO nanosheets hybrid structure, is reported. After detailed characterizations, the vapor sensing potentiality of this sensor was tested for the detection of ethanol. The ethanol sensor offered the response magnitude of 89% (100 ppm concentration) with response and recovery time of 12 s/29 s, respectively. Due to excessively high number of active sites for VOC interaction, with high yield synthesis process and appreciably high carrier mobility, this has paved the way for developing future generation, miniaturized and flexible (wearable) vapor sensor devices, meeting the multidimensional requirements for traditional and upcoming (health/medical sector) applications. The underlying mechanistic framework for vapor sensing, using this hybrid junction, is explained with the Energy Band Diagram.

Characteristics and Electronic Band Alignment of a Transparent p-CuI/n-SiZnSnO Heterojunction Diode with a High Rectification Ratio

Transparent p-CuI/n-SiZnSnO (SZTO) heterojunction diodes are successfully fabricated by thermal evaporation of a (111) oriented p-CuI polycrystalline film on top of an amorphous n-SZTO film grown by the RF magnetron sputtering method. A nitrogen annealing process reduces ionized impurity scattering dominantly incurred by Cu vacancy and structural defects at the grain boundaries in the CuI film to result in improved diode performance; the current rectification ratio estimated at ±2 V is enhanced from ≈106 to ≈107. Various diode parameters, including ideality factor, reverse saturation current, offset current, series resistance, and parallel resistance, are estimated based on the Shockley diode equation. An energy band diagram exhibiting the type-II band alignment is proposed to explain the diode characteristics. The present p-CuI/n-SZTO diode can be a promising building block for constructing useful optoelectronic components such as a light-emitting diode and a UV photodetector.

Annealing effects on structural and photovoltaic properties of the dip-SILAR-prepared bismuth oxyhalides (BiOI, Bi7O9I3, Bi5O7I) films

Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature and decent optical properties. This study mainly deals with clarifying the effects of phase transformations on the structure, optical, and electrical properties of BiOI thin film prepared via dip-successive ionic layer adsorption and reaction (SILAR) method at different annealing temperatures ranging from 100 to 400 °C. Therefore, significant phase transformations (i.e., the existence of Bi7O9I3 and Bi5O7I have been confirmed at 300 °C and 400 °C, respectively) appeared in the produced films, which were mainly due to the change of annealing temperatures. The experimental results confirmed that produced films achieved the maximum current density and efficiency and minimum current density and efficiency at 100 °C and 400 °C, respectively. Experimental results were also showed that with increasing the annealing temperature from 100 to 400 °C, the indirect bandgap risen from 1.77 to 2.96 eV while the crystallite size decreased from 17.62 to 12.99 nm. The energy band diagram with electrolyte explained the observed poor electrical properties during the phase transformation. Hence, this result will add positive impacts on the new information on findings for the dip-SILAR-prepared BiOI photovoltaic cells.