Metal-insulator-semiconductor-metal Research Articles

Rapid thermal annealing influences on microstructure and electrical properties of Mo/ZrO2/n-Si/Al MISM junction with a high-k ZrO2 insulating layer

The microstructural, chemical and electrical properties of Mo/ZrO2/n-Si/Al metal/insulator/semiconductor/metal (MISM) heterostructure with zirconium oxide (ZrO2) as an insulating layer are investigated. In comparison to the metal/semiconductor/metal (MSM) structure, the as-deposited and 600 °C annealed MISM heterostructures demonstrate outstanding rectifying performance and extremely low reverse leakage current. The as-deposited (0.98 eV) and 600 °C annealed MISM heterostructures (1.12 eV) have a higher barrier height (ɸb) than the MSM structure (0.70 eV), which indicates that the barrier height is influenced by the ZrO2 insulating layer. The results show that the ɸb values are improved for 600 °C annealed heterostructure. The forward bias C–V and G/w-V graphs exhibit anomalous peak/variations and three distinct regions called accumulation, depletion, and inversions with respect to the frequency that are attributed to the interface states and RS. The results indicate that ZrO2 film is an effective high-k oxide for the preparation of novel electronic device applications.

Accumulated charge measurement using a substrate with a restricted-bottom-electrode structure

Accumulated charge measurement (ACM) is a new experimental technique for organic semiconductors to evaluate the charge injection barrier at the semiconductor–metal interface directly using a metal–insulator–semiconductor–metal (MISM) capacitor. In this technique, the precise estimation of the electrostatic capacity of the insulator layer (CI) is required for the analysis. The information of this parameter is, in principle, included in the ACM data; however, it is not directly evaluated because of the error resulting from the charge-spreading effect in an organic MISM capacitor with an unrestricted electrode structure. Therefore, the CI in previous ACM experiments has been independently estimated from the area of the electrode. In this study, a novel design of a substrate with a restricted-bottom-electrode structure is reported. Using the newly designed substrate, it was possible to suppress the charge-spreading effect and successfully estimate precise values of CI directly from the ACM data. Subsequently, it was possible to evaluate the injection barriers at the metal-free phthalocyanine (H2Pc)–Ag and pentacene–Au interfaces, which were 0.4 and 0.15 eV, respectively. The built-in potentials in the semiconductor layer were also determined for the samples used in the measurement.

Frequency dispersion and dielectric relaxation in postdeposition annealed high-κ erbium oxide metal–oxide–semiconductor capacitors

The origin of frequency dispersion in postdeposition rapid thermal and furnace annealing treated Pt/Er2O3/Si/Pt, metal–insulator–semiconductor–metal (MISM) structure is systematically investigated. The cause of frequency dispersion in Pt/Er2O3/Si/Pt, MISM structure is attributed to the dielectric relaxation in high-κ Er2O3, after suppressing the extrinsic effects such as parasitic, lossy interfacial layer, surface roughness, polysilicon depletion, quantum confinement, and oxide tunneling. Further, the Havrilian–Negami law is used to model the frequency dispersion in postdeposition rapid thermal and furnace annealing treated Pt/Er2O3/Si/Pt, MISM structure up to 250 kHz. It is suggested that to obtain an accurate capacitance value, the dissipation factor must be minimum for the MISM structure with nanometer scale oxides/insulators. Additionally, a methodology is proposed for simple and efficient correction of measured capacitance from capacitance–voltage and capacitance–frequency characteristics. Moreover, the flatband voltage shift/hysteresis, frequency dependent border traps are estimated ∼0.45 V, ∼3.35 × 1012 traps/cm2 and ∼0.18 V, ∼1.84 × 1012 traps/cm2 for postdeposition rapid thermal and furnace annealing treated Pt/Er2O3/Si/Pt, MISM structures, respectively. Therefore, postdeposition furnace annealing treatment is superior to achieve high-quality high-κ Er2O3 (κ ∼16), with low frequency dispersion of ∼9% up to 250 kHz and minimal hysteresis (∼0.18 V) for next-generation complementary metal–oxide–semiconductor technology.

Electro-plasmonic 2 × 2 channel-routing switch arranged on a thin-Si-doped metal/insulator/semiconductor/metal structure.

Plasmonics as a new field of chip-scale technology is the interesting substrate of this study to propose and numerically investigate a metal/insulator/semiconductor/metal (MISM)-structure 2×2 plasmonic routing switch. As a planar subwavelength arrangement, the presented design has two npn-doped side-coupled dual waveguides whose duty is to route the propagating surface plasmon polaritons through the device. Relying on the MISM structure, which has a MOS-like thin-film arrangement of typically 45 nm doped silicon covered by a layer of 8 nm thick HfO(2) gate insulator, the routing configuration is electrically addressed based on the carrier-induced plasma dispersion effects as an external electro-plasmonic switching control. Finite-element-method-conducted electromagnetic simulations are employed to evaluate the switch optical response at telecom wavelength of λ=1550 nm, due to which the balanced operation measure of extinction ratios larger than 10 dB and insertion losses of around -1.8 dB are obtained for both channels of CROSS and STRAIGHT. Compared with other photonic and plasmonic switching counterparts, this configuration, besides its potential for CMOS compatibility, can be utilized as a high-speed compact building block to sustain higher-speed, more miniaturized, and less consuming electro-optic routing/switching protocols toward complicated optical integrated circuits and systems.

Modeling of bipolar resistive switching of a nonlinear MISM memristor

This paper presents a novel mathematical model of the bipolar resistive switching (BRS) of the metal-insulator-semiconductor-metal (MISM) in a Pt/Ta2O5/TaOx/Pt memristor. The proposed model is based on quantum mechanics and describes the BRS behaviour based on electron band theory and the physical characteristics of the metal-insulator-semiconductor (MIS) system. It also includes the physical characteristics of the insulator layer. The novelty of the proposed model lies in incorporating the tunnelling probability factor (TPF) between the semiconductor and the metal layers and therefore demonstrating its effect on the conduction mechanism. In addition, the effect of continuous variation of the interface traps densities and the ideality factor during BRS is modelled using the semiconductor properties and the characteristics of the MIS system. Thus, the model emphasizes the dependency of the memristor current on the physical characteristics of the insulator layer. Moreover, the electric field equation for the active region is derived for the MISM structure which is used, together with the Mott and Gurney rigid point-ion model and the Joule heating effect, to model the oxygen ion migration mechanism. Finally, the model also demonstrates the self-limiting growth of the doped region. Extensive simulation is carried out on the proposed model and the results are correlated against the experimental data which show that the proposed model is in good agreement with the physical characteristics of the MISM memristor.

Design and investigation of N-type metal/insulator/semiconductor/metal structure two-port electro-plasmonic addressed routing switch.

Relying on the new field of technology, plasmonics, we have proposed and investigated an N-type metal/insulator/semiconductor/metal (MISM)-based 1×2 plasmonic routing switch. However, the MISM structure has a 50 nm thick silicon core waveguide accompanied by a thin-film HfO(2) gate insulator, the electro-plasmonic addressing of the structure guides and routes the surface plasmon polaritons on a subwavelength regime. FEM-based electromagnetic simulations are prepared at a telecom wavelength of λ=1550 nm. Considering large electron concentration densities accumulated near the semiconductor/oxide interface, this switch presents extinction ratios of above 9 dB beside insertion losses of almost only -2 dB in competition with other plasmonic counterparts. Thus, the proposed compact and high-speed routing structure, featuring a minimum 1.1 μm waveguide length and the possibility of CMOS-compatible integrating, can be a well-engineered option for merging electronics and photonics on the same layout to sustain a speedier and more complicated optical network and integrated system-on-chips.

Factors affecting the stability and performance of ionic liquid-based planar transient photodetectors.

A novel planar architecture has been developed for the study of photodetectors utilizing the transient photocurrent response induced by a metal/insulator/semiconductor/metal (MISM) structured device, where the insulator is an ionic liquid (IL-MISM). Using vanadyl 2,3-naphthalocyanine, which absorbs in the communications-relevant near-infrared wavelength region (λ(max,film) ≈ 850 nm), in conjunction with C60 as a bulk heterojunction, the high capacitance of the formed electric double layers at the ionic liquid interfaces yields high charge separation efficiency within the semiconductor layer, and the minimal potential drop in the bulk ionic liquid allows the electrodes to be offset by distances of over 7 mm. Furthermore, the decrease in operational speed with increased electrode separation is beneficial for a clear modeling of the waveform of the photocurrent signal, free from the influence of measurement circuitry. Despite the use of a molecular semiconductor as the active layer in conjunction with a liquid insulating layer, devices with a stability of several days could be achieved, and the operational stability of such devices was shown to be dependent solely on the solubility of the active layer in the ionic liquid, even under atmospheric conditions. Furthermore, the greatly simplified device construction process, which does not rely on transparent electrode materials or direct electrode deposition, provides a highly reproducible platform for the study of the electronic processes within IL-MISM detectors that is largely free from architectural constraints.

Important Role of Polymorphs of Organic Semiconductors on the Reduction of Current Leakage in an Organic Capacitor

Leakage currents in two different capacitors, metal-insulator-metal (MIM) and metal-insulator-semiconductor-metal (MISM), are examined. The leakage current of the MIM capacitors with a Nylon6-TiO2 nanocomposite film was larger than that for the devices with a poly(4-vinylphenol) (PVP) buffer layer stacked on top of the composite film by a factor of 3.6. When the organic active layer of pentacene is introduced for the MISM capacitor, the reduction ratio of leakage current by stacking the PVP buffer layer onto the composite film is found to get more pronounced as much as about a factor of 25. Such a significant difference of reduction ratio for the leakage current between the MIM and MISM capacitors results from the different polymorphs of pentacene which are critically dictated by the morphological surface of the underlying layer.

Utilizing Photocurrent Transients for Dithiolene-Based Photodetection: Stepwise Improvements at Communications Relevant Wavelengths

Photodetection based on bis-(4-dimethylaminodithiobenzil)-Ni(II) (BDN), a representative and well-studied metal dithiolene that shows strong absorption in the near-infrared region of the electromagnetic spectrum, has been investigated. By adopting a metal/insulator/semiconductor/metal (MISM) structure, the peak photocurrent response to an oscillating light chain is increased by up to 50 times, compared to devices without an insulating layer. The transient form of the MISM photoresponse, while unsuitable for steady-state photodetection, can be used to detect periodic light signals of frequencies up to 1 MHz, and is thus applicable for optical communication. Further improvements have been realized by nanostructuring carbon black into the dithiolene layer, improving charge collection, and yielding detectivity of up to 1.6 × 10(11) Jones at wavelengths beyond the scope of silicon photodiodes. Such an architecture may allow the favorable absorption properties of other such metal dithiolenes to be harnessed, where their low charge carrier mobilities and short excitation lifetimes have previously limited their applicability to this field.

A thin‐film field‐emission cathode with Pt or Au interlayer between insulator and Zn0.75Mg0.25O

AbstractA thin‐film field‐emission cathode with Al/Ta2O5/(Pt or Au)/Zn0.75Mg0.25O/Pt–Au–Ag structure is proposed. Here, a Pt or Au interlayer is introduced between the insulator (Ta2O5) and semiconductor (Zn0.75Mg0.25O) layers in the metal‐insulator‐semiconductor‐metal (MISM) structure, in order to effectively control the interfacial electron‐energy‐state distribution. Consequently, the transmission current waveform of the proposed cathode becomes completely symmetric, while stable and uniform electron emission is reproducibly obtained. Maximum electron emission efficiency of 0.055% is obtained with a cathode using a Au interlayer and a Pt–Au–Ag top electrode. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nondestructive measurement of resistivity in bulk In xGa 1− xAs crystals

By using a nondestructive resistivity measurement (NDRM) technique, which is based on a Fourier analysis of charge response in a metal–insulator–semiconductor–metal (MISM) structure, the resistivity in bulk In x Ga 1− x As crystals has been measured. Two-dimensional (2-D) distribution map measured in a sample sliced along the growth direction in a graded composition ingot of In x Ga 1− x As crystal showed that the resistivity gradually decreased from 10 8 to 10 5 Ω cm with the increase of indium composition except in the seeding region. It was also found that there were inhomogeneous distributions of resistivity in the seeding region due to the diffusion of Si from the GaAs seed crsytal. Since the inhomogeneous distribution of resistivity reflects the growth conditions such as temperature distribution and melt flow, the nondestructive measurement of resistivity by the NDRM technique is useful for evaluating not only the crystal quality but also the growth technique in bulk In x Ga 1− x As crystals.

Electroluminescence of Devices with Thin-Film CaS:Ce3+, Cl- as the Active Luminescent Layer

Thin-film CaS:Ce3+, Cl- has been successfully employed for the first time as the active layer of an a.c. thin-film electroluminescent device. In order to compare the performance of a device using this material with that of devices employing the usual ZnS:Mn2+ material, MISM (metal-insulator-semiconductor-metal), ISM, and MSM devices were fabricated. Of these three devices, the singly-insulated device had the highest brightness, of 100 cd/m2, at a frequency of 5 kHz and a pulse height of 200 V. The brightness of this device is still lower than that of devices employing the usual ZnS:Mn2+. This is attributed to the smaller number of internal carriers and the smaller amount of carrier accumulation in the vicinity of the interface between the active luminescent layer and the insulating layer.