Frequency Capacitance Voltage Research Articles

Gamma irradiation-induced changes at the electrical characteristics of organic-based Schottky structures

We have studied electrical parameters of an Al/methyl violet/p-Si Schottky device by using current–voltage and capacitance–voltage–frequency measurements under γ irradiation at room temperature. Experimental results have shown that γ radiation gives rise to an increase in the barrier height, the ideality factor and the interfacial state density, while the series resistance decreases by applied radiation.

The electrical measurements in poly(2-chloroaniline) based thin film sandwich devices

Al/P2ClAn(CH 3COOH)/p-Si/Al structure has been obtained by evaporation of the polymer P2ClAn(CH 3COOH) on the front surface of p-type silicon substrate, P2ClAn: the poly(2-chloroaniline). The P2ClAn emeraldine salt was chemically synthesized by using acetic acid (CH 3COOH). It has been seen that the current–voltage characteristics of the heterojunction obey to space charge-limited current model. Furthermore, P2ClAn(CH 3COOH) was characterized by using Fourier Transform Infrared (FTIR) and Ultraviolet–Visible (UV–Vis) spectroscopies. An average value of μ, 2.43 × 10 − 5 cm 2 V − 1 s − 1 , was obtained for the mobility of the P2ClAn(CH 3COOH); this value is in agreement with the value of about 10 − 4 cm 2 V − 1 s − 1 given for the conjugated polymeric thin films in the literature. Low capacitance–voltage–frequency and conductance–frequency measurements have been made at the voltages of 0.00, 0.02 and 0.30 V in the frequency range of 100 Hz–2.0 MHz. An average value of 7.91 × 10 11 cm − 2 eV − 1 for interface state density has been obtained from the frequency–capacitance characteristics.

Aging effects on the interface state density obtained from current–voltage and capacitance–frequency characteristics of polypyrrole/p‐Si/Al structure

AbstractA metallic polypyrrole film has been directly formed on a p‐type Si substrate by means of an anodization method under conditions of constant current density by an electrolyte being held at a constant temperature of 55°C that was composed of 0.40M pyrrole and 0.10M tetrabutylammonium tetrafluoroborate. An aluminum electrode was used as an ohmic contact. The polypyrrole/p‐Si/Al structure has clearly demonstrated rectifying behavior by the current–voltage curves studied at room temperature. The capacitance–voltage–frequency curves of the structure have been measured at different frequencies at room temperature in dark. To observe the effect of the aging, the measurements were also repeated 7, 15, 30, 60, and 90 days after fabrication of the polypyrrole/p‐Si/Al Schottky diode. During the whole measurement process, the probe of holder on sample was fixed to eliminate effects of surface inhomogeneity. The interface state density distribution curves of device have been obtained from forward bias current–voltage (I‐V) and capacitance–frequency (C‐f) characteristics as a function of aging time. From these curves, the exponential growth of the interface‐state density from midgap toward the top of the valence band is very apparent. The shape of the interface state density distribution curves from the forward bias I‐V characteristics are very similar to those obtained from C‐f. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2313–2319, 2006

Characterization of current–voltage ( I– V) and capacitance–voltage–frequency ( C– V– f) features of Al/SiO 2/p-Si (MIS) Schottky diodes

The current–voltage ( I– V) characteristics of metal–insulator–semiconductor Al/SiO 2/p-Si (MIS) Schottky diodes were measured at room temperature (300 K). In addition, capacitance–voltage–frequency ( C– V– f) characteristics are investigated by considering the interface states ( N ss) at frequency range 100 kHz to 1 MHz. The MIS Schottky diode having interfacial insulator layer thickness of 33 Å, calculated from the measurement of the insulator capacitance in the strong accumulation region. At each frequency, the measured capacitance decreases with increasing frequency due to a continuous distribution of the interface states. From the I– V characteristics of the MIS Schottky diode, ideality factor ( n) and barrier height ( Φ b) values of 1.766 and 0.786 eV, respectively, were obtained from a forward bias I– V plot. In addition, the interface states distribution profile as a function of ( E ss − E v) was extracted from the forward bias I– V measurements by taking into account the bias dependence of the effective barrier height ( Φ e) for the Schottky diode. The diode shows non-ideal I– V behaviour with ideality factor greater than unity. This behaviour is attributed to the interfacial insulator layer, the interface states and barrier inhomogeneity of the device. As expected, the C– V curves gave a barrier height value higher than those obtained from I– V measurements. This discrepancy is due to the different nature of the I– V and C– V measurement techniques.

Determination of the distribution of electronic states in hydrogenated amorphous germanium by capacitance techniques

In this study we have determined the density of states below the Fermi level in hydrogenated amorphous germanium thin films by different capacitance techniques. In order to realize the goal, a-Ge:H films were first deposited on c-Ge substrates and later they were converted into Cu/c-Ge/a-Ge:H/Al sandwich structures. The current–voltage and capacitance–voltage–frequency characteristics of the samples were measured at various temperatures. The forward current initially increased exponentially with an increase in the applied voltage up to 0.25 V and then continued to increase nonexponentially. It was found that the carrier transport mechanism in the exponential region is limited by tunnelling and the activation energy of the junction was obtained from this region to be 0.57 eV. The gap states below the Fermi level were determined by three different methods: differential capacitance–voltage method, drive-level capacitance method and capacitance–energy method. Defect densities of the order of 2 × 1017 eV−1 cm−3 at just below the Fermi level have been obtained for our a-Ge:H samples.

Degradation of transparent metal–insulator–semiconductor solar cells due to heating effects

All the output parameters of the metal–insulator–semiconductor solar cells are degraded after heating. Also the dark current and the non-ideality factor are increased with heating. A reduction in the built-in potential has been detected. The capacitance–voltage–frequency measurements indicate the presence of interface states. These states are heavily occupied by electrons. Heating will increase the density of these states and consequently reduce the barrier height and the overall cell efficiency.

Semi-insulating GaAs as a relaxation semiconductor

It is shown that semi-insulating GaAs diodes exhibit all the qualitative electrical properties expected from a relaxation semiconductor. The degree of ideality increases after irradiation by neutrons for liquid encapsulated Czochralski and liquid phase epitaxy (LPE) material although LPE material is almost lifetimelike directly from manufacture. Experimental results are shown for current–voltage and capacitance–voltage frequency over a range of temperatures for samples in the low- and high-space charge limit conditions. The implications for commercial GaAs and other compound semiconductor devices are discussed.

The Impact of Rapid Thermal Annealing on the Properties of the Si (100)-SiO2 Interface

AbstractIn this work, we present results and analysis which demonstrate the influence of rapid thermal annealing (RTA) on the properties of the Si(100)-SiO2 interface. Polysilicon/oxide/silicon capacitor structures were subjected to RTA treatments, in a nitrogen ambient, over the temperature range 600-1050°C. The structures were examined using high frequency and quasi-static capacitance-voltage (CV) analysis to determine the interface state density profile across the energy gap immediately following the RTA step. The effect of hydrogen annealing subsequent to the RTA process is also presented. Based on the analysis of the interface state density profiles, it is suggested in this work, that RTA (T > 600°C) exposes silicon dangling bond (Pb) centres at the Si(100)-SiO2 interface. The implications of this work to the study of the Si-SiO2 interface, and the technological implications for silicon based MOS processes, are discussed.

A new wafer level reliability method for evaluation of ionic induced pmosfet drift effects

An ionic induced pMOSFET drift effect was investigated by deliberately enhancing the sodium concentration in interlevel dielectric layers.High frequency capacitance voltage and triangular voltage sweep (TVS) measurements as well as different bias temperature stress sequences were employed to show that the degradation is a two step process: sodium drift into active areas and charging of traps which were generated by sodium interactions with the semiconductor oxide interface.A special wafer level reliability method was developed which takes into consideration the two phase nature of the failure mechanism.

Diamond microelectronic gas sensors

Diamond-based microelectronic gas sensors using plasma enhanced chemical vapor deposition (PECVD) technology have been explored in our laboratory. This paper presents a new gas sensor using Pd/i-diamond structure for hydrogen detection. Hydrogen sensitivity of the device has been characterized and analyzed as a function of hydrogen partial pressure and temperature by using current-voltage (I–V) and capacitance-voltage-frequency (C-V-F) methods. The hydrogen sensitivity is high, reproducible, and repeatable over a wide temperature range including room temperature.

Formation and High Frequency CV-Measurements of Aluminum / Aluminum Nitride / 6H Silicon Carbide Structures

AbstractUndoped single crystalline aluminum nitride films were grown by metal organic chemical vapor deposition (MOCVD) at 1200 °C. The precursors used were trimethylaluminium (TMA) and ammonia (NH3) in a hydrogen carrier flow, at a pressure of 10 Torr. Silicon carbide substrates of the 4H or the 6H polytype with an epilayer on the silicon face, were used to grow the 200 nm thick A1N films. Aluminum was evaporated and subsequently patterned to form MIS capacitors for high frequency (400 kHz) capacitance voltage measurements at room temperature. It was possible to measure the structure and characterize accumulation, depletion and deep depletion. However, it was not possible to invert the low doped SiC epilayer at room temperature. From an independent optical thickness measurement the relative dielectric constant of aluminum nitride was calculated to be 8.4. The films were stressed up to 50 Volts (2.5 MV/cm) without breakdown or excessive leakage currents. These results indicate the possibility to replace silicon dioxide with aluminum nitride in SiC field effect transistors.

GaAs-based metal-insulator-semiconductor structures with low interface traps using molecular beam epitaxy and chemical vapor deposition

The performance of GaAs-based field-effect transistors (FETs) in switching and power applications can be enhanced substantially by employing a metal-insulator-semiconductor (MIS) structure. Attempts thus far have fallen short due to large interface trap concentrations, frequency dispersion, and hysteresis. By taking advantage of an in-situ process approach, we successfully gated insulator — GaAs structures with excellent interfacial properties. The structures utilize a Si interface layer or a composite Si/Ge layer grown on GaAs followed by a Si 3N 4 dielectric layer, all using a III–V molecular beam epitaxy (MBE) system connected by an ultrahigh vacuum transfer tube to an adjacent electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (CVD) system. This pseudo-in-situ feature in concert with recently implemented vacuum connected scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) allows investigations of the essential interface layers. High/low frequency capacitance-voltage, conductance versus frequency, and metal-insulator-semiconductor field-effect transistors (MISFETs) were used for a comprehensive characterization of the n-type MIS structures. From the stringent conductance measurements, interface state densities in the high 10 10 eV −1 cm −2 have been obtained. The hysteresis is about 150 mV for a field swing of +4 to −4 MV/cm. The frequency dispersion is nearly zero except near inversion where its value is about 100 mV. Self aligned gate depletion mode MISFETs having 3 μm gate lengths exhibited transconductances of 169 mS/mm for the pseudomorphic InGaAs channels and about 100–140 mS/mm for GaAs channels.

Electrical Characterization of Aluminum Nitride Films on Silicon Grown by Chemical Vapor Deposition

ABSTRACTAluminum nitride (AlN) films were grown on silicon (Si) substrates by chemical vapor deposition (CVD). The films were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The refractive index of the AlN films was determined by ellipsometry. Current-voltage and current-temperature characteristics were performed on metal-AlN-p+ Si structures with Pt, Au and Al as metal electrodes. The characteristics showed that at high field and high temperature the carrier conduction mechanism in the film was dominated by Frenkel-Poole emission. The relative dielectric constant of the AlN films was estimated to be 9.66+0.3 from capacitance-voltage-frequency (C-V-f) measurements on Au-AlN-p+ Si.

Nitrogen-Atom Bonding at Sio2/SI Interfaces in Metalinsulator-Semiconductor (MIS) Stacked Gates Made by Integration of Plasma Assisted Oxidation-Deposition and Rapid Thermal Processing

ABSTRACTSiO2 thin films were deposited by remote PECVD on Si surfaces exposed to species generated in O2/N2 and O2/NH3 plasmas. The surface chemistry was studied by Auger Electron Spectroscopy, AES, and the electrical properties of the SiO2/Si interface by high frequency and quasi-static Capacitance-Voltage, C-V, measurements. The AES results showed that Ccontamination was removed by exposure to both plasma-excited gas mixtures, but that N-atoms were incorporated into the SiO2 film, and Si-N bonds were formed at the SiO2/Si interface. C-V measurements indicated that the Si-N bonding structure, rather than the N-atom concentration, is critical in determining the interface electrical properties. The effects of Rapid Thermal Annealing, RTA, on the electrical properties of these SiO2/Si interfaces were also studied.

Nitrogen-Atom Bonding at SiO2/Si Interfaces in Metalinsulator-Semiconductor (MIS) Stacked Gates Made by Integration of Plasma Assisted Oxidation-Deposition and Rapid Thermal Processing

ABSTRACTSiO2 thin films were deposited by remote PECVD on Si surfaces exposed to species generated in O2/N2 and O2/NH3 plasmas. The surface chemistry was studied by Auger Electron Spectroscopy, AES, and the electrical properties of the SiO2/Si interface by high frequency and quasi-static Capacitance-Voltage, C-V, measurements. The AES results showed that Ccontamination was removed by exposure to both plasma-excited gas mixtures, but that N-atoms were incorporated into the SiO2 film, and Si-N bonds were formed at the SiO2/Si interface. C-V measurements indicated that the Si-N bonding structure, rather than the N-atom concentration, is critical in determining the interface electrical properties. The effects of Rapid Thermal Annealing, RTA, on the electrical properties of these SiO2/Si interfaces were also studied.