Negative capacitance in optically sensitive metal-insulator-semiconductor-metal structures
TL;DR: In this paper, the negative capacitance effect in back-to-back combination of a metal-insulator-semiconductor (MIS) structure and a metal semiconductor junction, which is fabricated on an n type Silicon-on-Insulator substrate is reported.
Abstract: We report a strong negative capacitance effect in back to back combination of a metal-insulator-semiconductor (MIS) structure and a metal-semiconductor junction, which is fabricated on an n type Silicon-on-Insulator substrate. The MIS capacitor comprises a SiO2-HfO2 insulator stack with embedded Pt nanoparticles. The capacitor undergoes a voltage stress process and thereby turns into a varactor and a photodetector. The negative capacitance is observed only under illumination in structures that employ a Schottky back contact. A symmetric double or an asymmetric single negative capacitance peak is observed depending on the nature of illumination. The phenomenon is attributed to the modulation of the semiconductor conductance due to photo generated carriers and their incorporation in trapping/de-trapping processes on interfacial and post filamentation induced defects in the insulator stack. The frequency range of the observed effect is limited to 100 kHz. Large ratios of light to dark and maximum to minimum ...
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TL;DR: In this article, the authors describe a technique to extract room temperature parameters of Schottky diodes based on single or double-terminal configurations whose barrier height is bias dependent.
Abstract: We describe a technique to extract room temperature parameters of Schottky diodes based on single or double-terminal configurations whose barrier height is bias dependent. This method allows us to extract the zero bias barrier height without specific knowledge of interface states or the existence of insulator layers at the metal-semiconductor boundaries. This technique enables us to establish the type of thermionic emission mechanism, limited by a bias dependent image force potential and/or diffusion, taking into account interfacial states or layers. This technique makes use of experimental current-voltage (I-V) characteristics measured at both bias polarities and different intensities of illumination and the corresponding voltage-dependent differential slope-voltage characteristics α=dln(I)/dln(V). This method is verified experimentally on a conventional p-Silicon based Schottky diode and on metal-semiconductor and metal-insulator-semiconductor diodes fabricated on n-silicon-on-insulator substrates. Pd/A...
15 citations
TL;DR: A simple device where the capacitance values can be modulated over a wide frequency range via the action of light and strain, while using cleanroom-compatible materials for fabrication is proposed, as well as for broadband impedance matching in radio frequency applications.
Abstract: We report on the evidence of negative capacitance values in a system consisting of metal-semiconductor-metal (MSM) structures, with Schottky junctions made of zinc oxide thin films deposited by Atomic Layer Deposition (ALD) on top of platinum interdigitated electrodes (IDE). The MSM structures were studied over a wide frequency range, between 20 Hz and 1 MHz. Light and mechanical strain applied to the device modulate positive or negative capacitance and conductance characteristics by tuning the flow of electrons involved in the conduction mechanisms. A complete study was carried out by measuring the capacitance and conductance characteristics under the influence of both dark and light conditions, over an extended range of applied bias voltage and frequency. An impact-loss process linked to the injection of hot electrons at the interface trap states of the metal-semiconductor junction is proposed to be at the origin of the apparition of the negative capacitance values. These negative values are preceded by a local increase of the capacitance associated with the accumulation of trapped electrons at the interface trap states. Thus, we propose a simple device where the capacitance values can be modulated over a wide frequency range via the action of light and strain, while using cleanroom-compatible materials for fabrication. These results open up new perspectives and applications for the miniaturization of highly sensitive and low power consumption environmental sensors, as well as for broadband impedance matching in radio frequency applications.
10 citations
TL;DR: In this paper, the authors examined the properties of Au/n-type GaAs metal-semiconductor (MS) structure in the different temperatures (80 −415 K) and + 5 −5 and − 5 − 5 voltages at 500 kHz.
Abstract: To investigation the phenomena of negative capacitance, we examined the capacitance–voltage (C–V), conductance–voltage (G/ω–V), and series resistance–voltage (RS–V) properties of Au/n-type GaAs metal–semiconductor (MS) structure in the different temperatures (80–415 K) and + 5 V and − 5 V voltages at 500 kHz. Because metal–semiconductor structures play a crucial role not only for compensating the electronic devices but also in determining different functionalities in nano-structure devices. In the forward bias region (after 1.50 V), capacitance–voltage curves show a negative capacitance behavior. The experimental results obtained showed that the C–V and G/ω–V curves are strong functions of temperature and bias voltage especially in the accumulation region, and also the strong negative capacitance behavior is always accompanied after + 1.5 voltage for capacitance–voltage curves at all temperatures. That is, C–V characteristics are exhibited a behavior transition from the positive to negative value after 1.5 V. As the C values decreases, G/ω increases in the positive voltage region. This negative behavior for C–V curves in the forward bias regions is explainable by considering the losses of interface charge at occupied regions below Fermi level due to impact ionization processes. Also, these behavior values can also be attributed to the increase in the polarization particularly at low temperatures and the introduction of more carriers in the structure.
9 citations
TL;DR: In this article, the authors investigated the capacitance-voltage characteristics of the Au/GaN/GaAs Schottky diode at room temperature for different frequencies, ranging from 1-kHz to 1-MHz.
Abstract: A nitride GaAs Schottky diode has been fabricated by the nitridation of GaAs substrates using a radio frequency discharge nitrogen plasma source with a layer thickness of approximately 0.7 nm of GaN. The capacitance–voltage (C–V) characteristics of the Au/GaN/GaAs structure were investigated at room temperature for different frequencies, ranging from 1 kHz to 1 MHz. The C–V measurements for the Au/GaN/GaAs Schottky diode were found to be strongly dependent on the bias voltage and the frequency. The capacitance curves depict an anomalous peak and a negative capacitance phenomenon, indicating the presence of continuous interface state density behavior. A numerical drift–diffusion model based on the Scharfetter–Gummel algorithm was elaborated to solve a system composed of the Poisson and continuities equations. In this model, we take into account the continuous interface state density, and we have considered exponential and Gaussian distributions of trap states in the band gap. The effects of the GaAs doping concentration and the trap state density are discussed. We deduce the shape and values of the trap states, then we validate the developed model by fitting the computed C–V curves with experimental measurements at low frequency.
7 citations
TL;DR: In this paper, the electrical and electro-optical characteristics of InAs/InP quantum dot (QD) laser diodes operating under continuous wave in the temperature range of 285 K to 353K were analyzed.
Abstract: This paper addresses the electrical and electro-optical characteristics of InAs/InP quantum dot (QD) laser diodes operating under continuous wave in the temperature range of 285 K to 353 K. Experimental data together with a model lead to an identification of the current flow mechanism in all the important drive regimes: very low bias (pre radiation regime), the exponential region of the current-voltage (I-V) curve, and in the nonlinear range where spontaneous and stimulated emission take place. The analysis discriminates among bias regions where the influences of the QD or the optical confinement layers dominate. Additionally, parameters and non-nonlinear processes under injection into the active region are described here for the first time. A high level injection (spontaneous, as well as stimulation emission regimes) results in non-linear I-V characteristics. Above the threshold, the recombination rate increases due to rapid “pinning” of the quasi-Fermi levels leading to an anomalous kink of the power exponent voltage characteristics. This manifests itself as a non-linear differential resistance increase even at elevated temperatures, up to 353 K. Capacitance voltage measurements reveal some peculiarities, namely, well defined capacitance peaks related to the QDs, hysteresis, and a low frequency negative capacitance phenomenon which enhance the laser potential functional capability.This paper addresses the electrical and electro-optical characteristics of InAs/InP quantum dot (QD) laser diodes operating under continuous wave in the temperature range of 285 K to 353 K. Experimental data together with a model lead to an identification of the current flow mechanism in all the important drive regimes: very low bias (pre radiation regime), the exponential region of the current-voltage (I-V) curve, and in the nonlinear range where spontaneous and stimulated emission take place. The analysis discriminates among bias regions where the influences of the QD or the optical confinement layers dominate. Additionally, parameters and non-nonlinear processes under injection into the active region are described here for the first time. A high level injection (spontaneous, as well as stimulation emission regimes) results in non-linear I-V characteristics. Above the threshold, the recombination rate increases due to rapid “pinning” of the quasi-Fermi levels leading to an anomalous kink of the power ex...
5 citations
References
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TL;DR: In this paper, a new single frequency technique was proposed for low surface state density determination in a range from 7 × 10 9 eV −1 cm −2 to 8 × 10 11 eV−1 cm−2.
Abstract: Fast interface state densities in the SiSi 2 system can be determined by measurements of the MIS capacitor admittance. Traditional detailed analysis require elaborate frequency dependent techniques. The more commonly used approximation techniques are difficult to interpret for interface state densities less than 1 × 10 11 eV −1 cm −2 . We present here a new single frequency technique as an approximation method which provides quantitative criteria on the quality of such interfaces. The data required are a single high frequency capacitance vs voltage measurement and a corresponding conductance vs voltage measurement. The validity of this technique is best demonstrated in a three-dimensional plot of conductance, frequency and voltage. This also gives added insight into the relationship between the temporal and thermodynamic properties of interface electronic states. Comparison of results using this approximation to more detailed treatments demonstrates the validity of this new method for low surface state density determination in a range from 7 × 10 9 eV −1 cm −2 to 8 × 10 11 eV −1 cm −2 .
646 citations
TL;DR: The performance of ZnO-based photodetectors is analyzed, discussing recent achievements, and comparing the characteristics of the variousPhotodetector structures developed to date.
Abstract: Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.
558 citations
TL;DR: In this article, a revised nomenclature for defects in MOS devices was developed, which clearly distinguishes the language used to describe the physical location of defects from that used to describing their electrical response.
Abstract: We have identified several features of the 1/f noise and radiation response of metal‐oxide‐semiconductor (MOS) devices that are difficult to explain with standard defect models. To address this issue, and in response to ambiguities in the literature, we have developed a revised nomenclature for defects in MOS devices that clearly distinguishes the language used to describe the physical location of defects from that used to describe their electrical response. In this nomenclature, ‘‘oxide traps’’ are simply defects in the SiO2 layer of the MOS structure, and ‘‘interface traps’’ are defects at the Si/SiO2 interface. Nothing is presumed about how either type of defect communicates with the underlying Si. Electrically, ‘‘fixed states’’ are defined as trap levels that do not communicate with the Si on the time scale of the measurements, but ‘‘switching states’’ can exchange charge with the Si. Fixed states presumably are oxide traps in most types of measurements, but switching states can either be interface tr...
444 citations
TL;DR: The results show that the piezo-phototronic effect can enhance the detection sensitivity more than 5-fold for pW levels of light detection.
Abstract: We demonstrate the piezoelectric effect on the responsivity of a metalsemiconductormetal ZnO micro-/nanowire photodetector. The responsivity of the photodetector is respectively enhanced by 530%, 190%, 9%, and 15% upon 4.1 pW, 120.0 pW, 4.1 nW, and 180.4 nW UV light illumination onto the wire by introducing a0.36% compressive strain in the wire, which effectively tuned the Schottky barrier height at the contact by the produced local piezopotential. After a systematic study on the Schottky barrier height change with tuning of the strain and the excitation light intensity, an in-depth understanding is provided about the physical mechanism of the coupling of piezoelectric, optical, and semiconducting properties. Our results show that the piezo-phototronic effect can enhance the detection sensitivity more than 5-fold for pW levels of light detection.
441 citations
TL;DR: In this article, the atomic layer deposition (ALD) was used to grow a thin platinum thin film at 300 °C by using methylcyclopentadienyl trimethylplatinum (MeCpPtMe3) and oxygen as precursors.
Abstract: Platinum thin films were grown at 300 °C by atomic layer deposition (ALD) using (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen as precursors. The films had excellent uniformity, low resistivity, and low-impurity contents. Structural studies by X-ray diffraction showed that the films were strongly (111) oriented. Growth rates of 0.45 A cycle-1 were obtained with 4 s total cycle times. The film thickness was found to linearly depend on the number of the reaction cycles. Also, the possible reaction mechanism is discussed.
407 citations