Semiconductor Resistance Research Articles

SPICE analysis of the charge division in resistive semiconductor nanowire diodes

In this paper we present an analysis of the charge division method in semiconductor nanowire Schottky diodes using an electrical model based on the SPICE simulation code. A semiconductor nanowire prototype that is simulated as an RC network and two readout electronic systems are modelled in order to understand its behaviour and to assess its application as a possible ionizing particle detector in clinical high-LET particle beams. We study the use of resistive charge division along the semiconductor nanowire to calculate the position of deposited charge generated by an ionizing particle as it crosses the nanodevice and to determine the minimal viable spatial resolution.Our aim is to demonstrate the charge division concept in resistivesemiconductor nanowire diodes, and to subsequently understand theperformance of these nanodevices as radiation sensors and address thedesign limitations of such an application.

RF Capacitive Spectroscopy for Contactless Measurements of Resistivity Profiles in Highly Resistive Semiconductor Wafers

In this paper, we present a contactless, capacitive method of estimating the resistivity profiles in the direction perpendicular to the semiconductor wafer using frequency domain impedance analysis. Employing a simple model, we show that the different resistivity distributions inside a wafer affect the frequency dependencies of the measured effective capacitance and the Q-factor. We also demonstrate how to estimate resistivity variation inside the sample from the experimental data: C(ω) and Q(ω).

Resistance switching in rejuvenated NaNbO3:Mn crystals

In this paper, the resistance switching effect has been studied in NaNbO3:Mn crystals. Samples were rejuvenated in ambient air, below and above antiferroelectric phase transition. Dielectric spectroscopy has exhibited weak dispersion. The influence of annealing on the electronic structure has been determined with the use of X-ray photoelectron spectroscopy. Na2s, Nb3d, O1s, and Mn2p lines of the aged as-grown crystal and the rejuvenated samples spectra have been analyzed. Nb4+ states observed in the samples point to the presence of oxygen vacancies in the surface layer. Na ions migrate toward the surface due to rejuvenation. Switching from an insulator high-resistance state to a semiconductor medium resistance and finally to a metallic-type low-resistance state has been observed. The results are discussed within the framework of the extended defects model. We propose that the aliovalent Mn2+ dopant ions stabilize the oxygen vacancies and enable the resistive switching.

Impact ionization and large room-temperature magnetoresistance in micron-sized high-mobility InAs channels

We report on hot electron induced impact ionization and large room-temperature magnetoresistance (MR) in micron-sized channels of $n$-type high-mobility InAs $(\ensuremath{\mu}=3.3{\mathrm{m}}^{2}{\mathrm{V}}^{\ensuremath{-}1}{\mathrm{s}}^{\ensuremath{-}1}$ at $T=300\mathrm{K})$: the MR reaches values of up to 450% in magnetic fields of 1 T and applied voltages of \ensuremath{\sim}1 V and is weakly dependent on temperature. We present Monte Carlo simulations of the hot electron dynamics to account for the large MR and its dependence on the sample geometry and applied electric and magnetic fields. Our work demonstrates that the impact ionization of electrons at room temperature, under small applied magnetic fields (1 T) and small voltages (1 V), can provide an extremely sensitive mechanism for controlling the electrical resistance of high-mobility semiconductors.

Method for characterizing the contact resistance of metal-vanadium dioxide thin film interfaces

The standard method for determining the contact resistance of planar metal-semiconductor interfaces can underestimate the true contact resistance under normal operating conditions, as it relies on the resistivity of the semiconductor material remaining constant during measurement. However, the strong temperature dependence of the resistivity of VO2 requires a modified approach that maintains a constant power density dissipated within the film to account for Joule heating. We develop a method for measuring contact resistance in semiconductors with a high thermal coefficient of resistivity, demonstrate this method with an example, and compare the results with the standard technique.

The Molecular Controlled Semiconductor Resistor: A Universal Sensory Technology

AbstractWe review some of the sensors based on the molecular control semiconductor resistor (MOCSER) technology. The technology can be applied for developing highly sensitive and selective molecular sensors that operate both in gas and in liquid environments. Specifically, we describe here a set of GaAs gas‐phase sensors based on an array constructed from several elements, each coated with a different sensing molecule. Coating the same semiconductor device with an ultrathin polymer layer also allows the use of the device in a harsh liquid environment and in performing measurements in physiological liquids. Hence, the MOCSER‐based platform opens the way for producing inexpensive, easy to use, and robust sensors for a wide variety of applications.

Investigation of the Nanodiagnostics Probe Modes for Semiconductor Resistivity Measurements by Atomic Force Microscopy

The work presents the results of theoretical and experimental investigations of the features and nanodiagnostics probe modes for semiconductors resistivity measurements by current technique of atomic force microscopy and by using test silicon samples with known resistivities (0.01 Ωcm, 1 Ωcm, 5 Ωcm, 10 Ωcm). It is shown that the measured resistivity data in air and in ultrahigh vacuum (10-8 Pa) is 166 Ωcm and 10 Ωcm, respectively, for the sample with ρ = 10 Ωcm of theoretically predicted resistivity. We showed that reducing of the measurements reliability in air, due to the local anodic oxidation of the substrate surface. Experimental studies of the influence of cantilever load forces (0.3 to 6.0 μN) to the samples surface on the current distribution are presented. Based on the experimental results we developed a mathematical model for determining the resistivity of semiconductor materials by current technique of atomic force microscopy. The results are useful to the development of probe methods for nanoelectronic devices analysis by atomic force microscopy.

A Theoretical Study on Photocatalytic Fuel Cell

This paper presents a theoretical study which investigates the detail potential loss within photocatalytic fuel cell (PFC). Ohmic loss in PFC contributes to 24% potential loss since the large electrical resistance of semiconductor. It is found that Schottky barrier height plays an important role on performance of PFC, and Schottky barrier height of 0.6eV is preferred for PFC operation. Moreover, current will be enhanced with the activity of photocatayst increasing.

Application of reactor neutrons to the investigation of the radiation resistance of semiconductor materials of Group III–V and sensors

The investigation of the radiation resistance of Group III–V semiconductor materials is an important and urgent problem. Magnetic sensors based on radiation resistant semiconductor materials are widely used in magnetomeasuring systems of thermonuclear industrial and experimental reactors. The basic approaches to the study of semiconductor materials under conditions of neutron irradiation and the results of some experiments on testing indium-containing semiconductor materials InSb, InAs, and their alloys InAsxSb1 − x are presented. The presented experience of the development of equipment for on-line testing of materials and magnetic diagnostic sensors under radiation conditions can be used for testing a wide range of materials under conditions close to those of the ITER and other thermonuclear reactors.

Temperature sensing behavior of poly(3,4-ethylenedioxythiophene) thin film

Temperature sensing behavior of poly(3,4-ethylenedioxythiophene) (PEDOT) thin film was investigated at the temperature range of −20°C to 60°C. PEDOT thin films were fabricated by in situ polymerization, where 3,4-ethylenedioxythiophene (EDOT) and ferric p-toluene sulfonate (FTS) were used as a monomer and an oxidant, respectively. The monomer and the oxidant solutions in 1-butanol were prepared separately and mixed just before in situ polymerization. The mixed solution was cast on a substrate and polymerization was carried out at 70°C for 30min, followed by washing with methanol and drying under vacuum.Resistance change of PEDOT film with temperature was monitored using two probe method. It was observed that resistance of PEDOT film monotonically decreased with increasing temperature, confirming a typical temperature dependence of the electrical resistance of semiconductors with negative temperature coefficient (NTC). However, resistance of PEDOT thin film was not stable with repeated heating and cooling. Resistance at the same temperature increased with repeated heating and cooling cycles. We found that stability of PEDOT thin film could be significantly improved by heat treatment of PEDOT film at 150°C for 1h and sealing the PEDOT thin film. Temperature-dependent resistance of the stabilized PEDOT thin film could be fitted to the Steinhart–Hart equation from −20°C to 60°C range even after repeated cycles, suggesting its potential application as a flexible thin film thermistor.

Analysis of the on-state resistance of photoconductive semiconductor switches in the non-linear mode

Excellent performances such as ultrafast rise-time, low jitter, good synchronization and high electric-field strength make photoconductive semiconductor switches (PCSSs) have a wider prospect of application. Among other parameters, it is very important to evaluate the on-state resistance of the PCSS. In this paper, the influence of bias voltage, on-state current and trigger position on the on-state resistance of GaAs PCSS is described. We extracted the relationship between the elements mentioned above and the on-state resistance from our experimental data. The on-state resistance decreases with increasing bias voltage as well as increasing on-state current. The best trigger position was evaluated to be on the cathode. The on-state resistance increases as the trigger position shifts from cathode to anode gradually. The experimental results are further discussed in this paper.

Resistance in single-walled carbon nanotube networks formed on gold nanoparticle templates

The temperature dependence features of a typical intrinsic semiconductor resistance were used to study the resistances in single-walled carbon nanotube (SWNT) networks formed on gold nanoparticle (AuNP) templates, using the resistance–temperature relations in the temperature range from 440 to 570 K. The SWNTs were synthesized using the chemical vapour deposition method, with ethanol as a carbon source and cobalt particles as the catalyst. The synthesis was performed at 1073 K, for a duration of 60 min. It was found that the negative temperature coefficients and the energy gaps, which indicated the degree of semiconductor behaviour, increased with increasing sample starting resistance. However, at the same sample starting resistance, the degree of semiconductor behaviour increased with increasing AuNP number density, resulted from the change in the effective diameter of the semiconducting SWNTs of the sample, which occurred because of the effects of the AuNP number density.

Applications of Nanostructured Materials as Gas Sensors

Gas detection instruments are increasingly needed for industrial health and safety, environmental monitoring, and process control. To meet this demand, considerable research into new sensors is underway, including efforts to enhance the performance of traditional devices, such as resistive metal oxide sensors, through nanoengineering. The resistance of semiconductors is affected by the gaseous ambient. The semiconducting metal oxides based gas sensors exploit this phenomenon. Physical chemistry of solid metal surfaces plays a dominant role in controlling the gas sensing characteristics. Metal oxide sensors have been utilized for several decades for low-cost detection of combustible and toxic gases. Recent advances in nanomaterials provide the opportunity to dramatically increase the response of these materials, as their performance is directly related to exposed surface volume. Proper control of grain size remains a key challenge for high sensor performance. Nanoparticles of SnO2have been synthesized through chemical route at 5, 25 and 50°C. The synthesized particles were sintered at 400, 600 and 800°C and their structural and morphological analysis was carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The reaction temperature is found to be playing a critical role in controlling nanostructure sizes as well as agglomeration. It has been observed that particle synthesized at 5 and 50°C are smaller and less agglomerated as compared to the particles prepared at 25°C. The studies revealed that particle size and agglomeration increases with increase in sintering temperature. Thick films gas sensors were fabricated using synthesized tin dioxide powder and sensing response of all the sensors to ethanol vapors was investigated at different temperatures and concentrations. The investigations revealed that sensing response of SnO2nanoparticles is size dependent and smaller particles display higher sensitivity. Table of Contents

Temperature Dependence of Annealed and Nonannealed HEMT Ohmic Contacts Between 5 and 350 K

HEMT performance critically depends on contact resistance, particularly in cryogenic applications, where the semiconductor resistance contributions are reduced, thanks to lower optical phonon scattering rates. The literature offers little about the temperature dependence of contact resistances in HEMTs. We report a temperature-dependent comparison of the annealed and nonannealed ohmic contacts for low-noise InP HEMTs. Contact resistances of annealed Ge/Au/Ni/Au and nonannealed Ti/Pt/Au ohmic contacts were characterized as a function of temperature between 5 and 350 K. Side-by-side comparison exposes the differences of nonannealed versus annealed structures with respect to the contact and sheet resistance. Whereas both contact types show equivalent performances at cryogenic temperatures for recessed cap structures reminiscent of practical HEMTs, our annealed contacts display a significant increase in contact resistance with increasing temperature, in marked contrast to the near temperature independence found in our nonannealed contacts. The finding is of importance since the source resistance directly enters the transistor minimum noise figure <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> in field-effect transistors. Additional contributions to the parasitic sheet resistance of ohmic, overlay, and electroplated interconnect metals are also characterized as a function of temperature.

Gas Dielectric Transistor of CuPc Single Crystalline Nanowire for SO2 Detection Down to Sub‐ppm Levels at Room Temperature

Sulfur dioxide (SO 2 ) is one of the most dangerous air pollutants that impair environment and human health. SO 2 in air is released during the burning of fossil fuels and plays one major role in the formation of acid rain. The repeated exposure to low levels of SO 2 can cause permanent pulmonary impairment for humans. [ 1 ] The long and short-term exposure limits for SO 2 gas are 2 and 5 ppm, respectively, [ 1 , 2 ] and the U. S. Environmental Control Agency has set the acceptable limit for SO 2 in ambient air at a level of 0.5 ppm. [ 3 ] It is of great importance to measure low concentration of SO 2 in air accurately and fast for human health protection and air-quality monitoring. Semiconductor resistor sensors are, for more than 30 years, one of the most common used gas sensors to detect toxic and fl ammable gases such as NO 2 , H 2 S, CO, NH 3 , and H 2 because of their distinguished merits such as low cost, long lasting, high sensitivity, and good reliability, etc. [ 4 ] Organic fi eld-effect transistor (OFET) is another alternative semiconductor sensing technology with advantages over resistors, and has attracted much attention only recently. [ 5 ] The sensitivity can be dramatically enhanced by changing the source-drain current ( I SD ) of OFET when operating the sensors in the sub-threshold regime, as a result of the current modulation by the extra gate electrode. [ 6 ] Another advantage of OFET sensors is that the sensing response can be enhanced by integrating them in oscillator and adaptive amplifi er circuits. [ 7 ] These advantages combined with low cost and light weight of organic semiconductors ensure that OFET sensors have attracted much attention for the detection of a wide range of gases. [ 8 ]

Enabling Long-Term Operation of GaAs-Based Sensors

A coating scheme was developed for enabling the operation of a GaAs-based Molecular Controlled Semiconductor Resistor (MOCSER) under biological conditions. Usually GaAs is susceptible to etching in an aqueous environment. Several methods of protecting the semiconductor based devices were suggested previously. However, even when protected, it is very difficult to ensure the operation of a GaAs-based electronic sensor in aqua solution for long periods. We developed a new depositing scheme of (3-mercaptopropyl)-trimethoxysilane (MPTMS) on GaAs substrate consisting of two separate steps. The first involves chemisorption of a dense primary MPTMS layer on the substrate, whereas in the second, a thin MPTMS polymer layer is deposited on the already adsorbed layer, resulting in a 15 - 29 nm thick coating. We show that applying the new MPTMS deposition procedure to GaAs-based MOCSER devices allows up to 15 hours of continuous electrical measurements and stable performance of the sensing device in harsh biological environment. The new protection allows implementing GaAs technology in bioelectronics, particularly in biosensing.

Assessment of Temperature-Dependent Conductivity Effects on the Thermal Spreading/Constriction Resistance of Semiconductors

Assessment of Temperature-Dependent Conductivity Effects on the Thermal Spreading/Constriction Resistance of Semiconductors

Assessment of Temperature-Dependent Conductivity Effects on the Thermal Spreading/Constriction Resistance of Semiconductors

Thermal spreading resistance takes placewhenever heat flow leaves a source of finite area and enters awider area. The present study aims to obtain the thermal spreading/constriction resistance models of some semiconductor materials with temperature-dependent thermal conductivity. A steady-state nonlinear heat conduction equation of the problem is transformed into the Laplace equation via the Kirchhoff transformation. The concepts of individual isotropic half-space and heat-flux tube are used in this study. The spreading resistances of the semiconductor materials in arbitrary temperature andheat-flux ranges are compared to each other. Results indicate that spreading/ constriction resistance is affected by the temperature-dependent conductivity of semiconductor materials. The conductivity dependence of spreading/constriction resistance becomesmore significant as the difference between the temperatures of contact surface and convenient thermal sink becomes more evident.

What causes high resistivity in CdTe

Shallow donors are often introduced into semiconductor materials to enhance n-type conductivity. However, they can sometimes also be used to obtain compensation between donors and acceptors, resulting in high resistivity in semiconductors. For example, CdTe can be made semi-insulating by shallow donor doping. This is routinely done to obtain high resistivity in CdTe-based radiation detectors. However, it is widely believed that the shallow donor alone cannot be responsible for the high resistivity in CdTe. This is based on the argument that it is practically impossible to control the shallow donor doping level so precisely that the free carrier density can be brought below the desired value suitable for radiation detection applications. Therefore, a deep native donor is usually assumed to exist in CdTe and pin the Fermi level near midgap. In this paper, we present our calculations on carrier statistics and energetics of shallow donors and native defects in CdTe and illustrate different donor-specific mechanisms for achieving carrier compensation. Our results show that the shallow donor can be used to reliably obtain high resistivity in CdTe without requiring additional deep donors. Since radiation detection applications require both high resistivity and good carrier transport, one should generally use shallow donors and shallow acceptors for carrier compensation and avoid deep centers that are effective carrier traps. This study highlights how the interaction between impurities and native defects intricately affects the Fermi level pinning in the semiconductor band gap and the associated resistivity of the material.

AC electrical properties of FeIn2S4

The frequency and temperature dependences of the ac capacitance and resistivity of FeIn2S4 semiconductors are studied. Resonances are observed at certain temperatures in the frequency range (2.5–5.0) × 105 Hz. The permittivity of the crystals and the activation energy of charge carriers are determined. It is found that electrical conduction in the given temperature interval is governed by an activation mechanism. The activation energy is frequency-dependent, because the relaxation time of barrier layers decreases with rising frequency.