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ZnS/p-Si heterojunction diode has been successfully fabricated by depositing the ZnS thin films on p-type Si substrates using thermionic vacuum arc technique (TVA). The structural analysis was performed with X-ray diffraction (XRD) and Atomic force microscopy (AFM). The results revealed that ZnS thin film demonstrates nano-crystalline behavior with very smooth and homogeneous surface properties. The type was determined as n-type and the carrier concentration was found approximately 3.1 +/- 10(17) cm(-3) of the ZnS thin film by means of Hall Effect measurement. The dark current-voltage (I-V) and the capacitance- voltage (C-V) measurements with different frequencies were performed to determine the characteristics of the ZnS/p-Si heterojunction diode at room temperature. I-V results show that the diode has a good rectifying characteristic with excellent rectification ratio. The electrical parameters of the diode have been obtained by using current transport mechanism. It was found that the barrier height calculated from dark I-V measurements is in good agreement with the value obtained from C-V measurements at a frequency of 1.5 MHz. The series resistance and the built in potential of the fabricated diode were calculated as 3.6 k Omega and 0.7 V using Cheung and Cheung's equation and C-V measurement, respectively. The low cost and effective film production method were utilized to fabrication of heterojunction diode and to investigate characteristics.

In this paper, AlN thin films with two different thicknesses, i.e., 7 and 47 nm, were deposited at 200 °C on p-type Si substrates by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia. To investigate the electrical characteristics of these AlN films, MIS capacitor structures were fabricated and characterized using current-voltage and high-frequency (1 MHz) capacitance-voltage measurements. The results showed that the current transport mechanism under accumulation mode is strongly dependent on the applied electric field and thickness of the AlN film. Possible conduction mechanisms were analyzed, and the basic electrical parameters were extracted and compared for AlN thin films with different thicknesses. Compared with 7-nm-thick film, a 47-nm-thick AlN film showed a lower effective charge density and threshold voltage along with a higher dielectric constant.

Among perovskite oxide materials, BaSrTiOx (BST) has attracted great attention due to its potential applications in oxide-based electronics. However, reliability and efficiency of BST thin films strongly depend on the precise knowledge of the film microstructure, as well as optical and electrical properties. In the present work, BST films were deposited at room temperature using radio frequency magnetron sputtering technique. The impact of deposition pressure, partial oxygen flow, and post-deposition annealing treatment on film microstructure, surface morphology, refractive index, and dielectric constants were studied by X-ray diffraction, scanning electron microscopy, spectrophotometry, ellipsometry, photoluminescence, as well as capacitance-voltage measurements. Well-adhered and uniform amorphous films were obtained at room temperature. For all as-deposited films, the average optical transmission was similar to 85% in the VIS-NIR. spectrum. The refractive indices of BST films were in the range of 1.90-2.07 (lambda = 550 nm). Post-deposition annealing at 800 degrees C for 1 h resulted in polycrystalline thin films with increased refractive indices and dielectric constants, however reduced optical transmission values. Frequency dependent dielectric constants were found to be in the range of 46-72. However, the observed leakage current was relatively small, about 1 mu A. The highest FOM values were obtained for films deposited at 0.67 Pa pressures, while charge storage capacity values increased with increased deposition pressure. Results show that room-temperature grown BST films have potential for device applications.

In the present work, we report a novel citrate-selective sensor based on iron (III) phthalocyanine chloride-C-monoamido-Poly-n-Butyl Acrylate (Fe(III)MAPcCl-P-n-BA) modified silicon nitride and Ion sensitive field effect transistor (ISFET) structures for the electrochemical determination and estimation of the pathophysiological range of citrate. The developed capacitive sensor based on Fe(III)MAPcCl-P-n-BA had a Nernstian sensitivity of (−20.2 ± 1.3) mV/decade with a detection limit of about 7 × 10 −7 M and a linear range from 10 −6 M to 10 −1 M (RSD = 6.2%). Then, the performance of the Fe(III)MAPcCl-P-n-BA functionalized ISFET structure towards the detection of citrate has been investigated. A Nernstian sensitivity of about (−19.8 ± 1.0) mV/decade in the range from 10 −6 M to 10 −1 M was achieved (RSD = 4.8%) which covered the pathologically important clinical range of citrate. The detection limit was about 4 × 10 −7 M. The number of available recognition sites N s and the complexation constant pK were calculated using the enhanced site binding model. A side by side comparison of the developed chemical sensors based on electrolyte-insulator-Semi conductor (EIS) and ISFET structures showed similar characteristics which proves the successful miniaturization of the semiconductor based transducer. The obtained experimental data of the Fe(III)MAPcCl-P-n-BA functionalized ISFET structure were used to validate the TopSPICE ISFET/MEMFET macromodel. The obtained theoretical sensitivity was in good agreement to the experimental one which proves the successful design of the developed ISFET/MEMFET macromodel.

Electrical properties of Ta/n-Si and Ta/p-Si Schottky barrier diodes obtained by sputtering of tantalum (Ta) metal on semiconductors have been investigated. The characteristic parameters of these contacts like barrier height, ideality factor and series resistance have been calculated using current voltage (I-V) measurements. It has seen that the diodes have ideality factors more than unity and the sum of their barrier heights is 1.21 eV which is higher than the band gap of the silicon (1.12 eV). The results have been attributed the effects of inhomogeneities at the interface of the devices and native oxide layer. In addition, the barrier height values determined using capacitance-voltage (C-V) measurements have been compared the ones obtained from I-V measurements. It has seen that the interface states have strong effects on electrical properties of the diodes such as C-V and Rs-V measurements. © 2010 Elsevier Ltd. All rights reserved.

Charge-trapping memories such as SONOS and MONOS have attracted considerable attention as promising alternatives for next-generation flash memories due to dielectric layer’s scalability, process simplicity, power economy, operation versatility. Nevertheless, the continued miniaturization of the devices forces an application of high-k dielectrics. In this work high-k stacked dielectric structures based on the combination of Hf-based and SiNx materials were fabricated. Their structural and electrical properties versus deposition conditions are studied by means of FTIR-ATR and high-resolution TEM techniques. All samples demonstrated smooth surface (roughness below 1 nm) and abrupt interfaces between the different stacked layers. No crystallization of Hf-based layers was observed after annealing at 800°C for 30 min, demonstrating their amorphous nature and phase stability upon annealing. Electrical characterization was carried out for all samples through capacitance-voltage (C-V) measurements of MIS capacitors. Uniform C-V characteristics were measured along the samples for all stacks. Besides, significant flat-band hysteresis due to charging of the stacks caused by carrier injection from the substrate was observed for the structures with pure HfO2 layers.

The frequency dependent irradiation influences on Sm2O3 MOS capacitors have been investigated and possible use of Sm2O3 in MOS-based radiation sensor was discussed in this study. To examine their gamma irradiation response over a range of doses, the fabricated MOS capacitors were irradiated up to 30 grays. Capacitance-Voltage (C-V) measurements were recorded for various doses and the influences of irradiation were determined from the mid-gap and flat-band voltage shifts. In addition, the degradations of irradiation have been studied by impedance based leakage current-voltage (J-V) characteristics. The results demonstrate that J-V characteristics have not been significantly change by irradiation and implying that the excited traps have a minor effect on current for given dose ranges. However, the frequency of applied voltage during. the C-V measurements affects the irradiation response of devices, significantly. The variations on the electrical characteristics may be attributed to the different time dependency of acceptor and donor-like interface states. In spite of the variations on the device characteristics, low frequency measurements indicate that Sm2O3 is a potential candidate to be used as a dielectric layer in MOS based irradiation sensors. Orta Doğu teknik Üniversitesi Abant İzzet Baysal Üniversitesi (AİBÜ) Abant İzzet Baysal Üniversitesi (BAP. 2014.03.02.706) Türkiye Cumhuriyeti Kalkınma Bakanlığı (2012K120360)

The purpose of this study is to investigate the usability of ytterbium oxide (Yb2O3) as a sensitive region/gate oxide in metal oxide semiconductor (MOS) based dosimeters and to determine the advantages and disadvantages of this device relative to its alternatives. For this purpose, amorphous Yb2O3 films were grown on p type Si by radio-frequency magnetron sputtering and aluminum (Al) was used as front and back ohmic contacts of the capacitor. Yb2O3 MOS devices were irradiated incrementally to the total dose of 70 Gy by Co-60 radioactive source. The capacitance-voltage measurements were performed at low (100 kHz) and high (1 MHz) frequencies to examine the behavior of the traps. The sensitivity of the device for 70 Gy was obtained using flat band voltage shifts as 27.5 +/- 1.1 and 28.1 +/- 1.3 mV/Gy for 100 kHz and 1 MHz, respectively. The changes in the oxide trap charge densities in the studied dose between 0.5 and 70 Gy are in the ranges of (1.09 +/- 0.04) x 10(11)-(1.23 +/- 0.05) x 10(12) cm(-2) for 100 kHz and (-3.26 +/- 0.08) x 10(10)-(8.16 +/- 0.35) x 10(11) cm(-2) for 1 MHz. For both frequencies, there was no significant change in the interface trap charge densities over the applied dose and the density of these traps remained in order of 10(11) cm(-2) after each applied dose. The percentage fading were measured at only 1 MHz for evaluation of the device's dose storage capacity and the results varied from 4% (5 min) to -19% (50 min). An almost constant fading value was obtained after 20 min from irradiation. The capacitor's sensitivity was found to be higher than those of similar devices composed of HfO2, La2O3, SiO2, Sm2O3, and Y2O3. Yb2O3 would be a promising candidate for a new generation of MOS based radiation sensors. Türkiye Cumhuriyeti Kalkınma Bakanlığı - 2016K121110 Abant İzzet Baysal Üniversitesi - AIBU, BAP -.2014.03.02.765

In this work, 7.5 nm Ga2O3 dielectric thin films have been deposited on p-type (111) silicon wafer using plasma enhanced atomic layer deposition (PEALD) technique. After the deposition, Ga2O3 thin films were annealed under N-2 ambient at 600, 700, and 800 degrees C to obtain beta-phase. The structure and microstructure of the beta-Ga2O3 thin films was carried out by using grazing-incidence X-ray diffraction (GIXRD). To show effect of annealing temperature on the microstructure of beta-Ga2O3 thin films, average crystallite size was obtained from the full width at half maximum (FWHM) of Bragg lines using the Scherrer formula. It was found that crystallite size increased with increasing annealing temperature and changed from 0.8 nm to 9.1 nm with annealing. In order to perform electrical characterization on the deposited films, Al/beta-Ga2O3/p-Si metal-oxide-semiconductor (MOS) type Schottky barrier diodes (SBDs) were fabricated using the beta-Ga2O3 thin films were annealed at 800 degrees C. The main electrical parameters such as leakage current level, reverse breakdown voltage, series resistance (R-S), ideality factor (n), zero-bias barrier height (phi(Bo)), and interface states (N-SS) were obtained from the current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The RS values were calculated by using Cheung methods. The energy density distribution profile of the interface states as a function of (E-SS-E-V) was obtained from the forward bias I-V measurements by taking bias dependence of ideality factor, effective barrier height (phi(e)), and R-S into account. Also using the Norde function and C-V technique, phi(e) values were calculated and cross-checked. Results show that beta-Ga2O3 thin films deposited by PEALD technique at low temperatures can be used as oxide layer for MOS devices and electrical properties of these devices are influenced by some important parameters such as NSS, RS, and beta-Ga2O3 oxide layer. (C) 2014 Elsevier B.V. All rights reserved.

We report on a detailed investigation of the degradation of AlGaN/GaN Schottky diodes grown on silicon, submitted to high reverse-bias. The analyzed devices have a vertical structure; thanks to this feature, it was possible (i) to characterize the effects of stress by means of capacitance-voltage (C-V) measurements, therefore, identifying and localizing the trap states generated as a consequence of the stress tests; (ii) to accurately control the intensity and distribution of the electric field over stress time. Results indicate that stress induces an increase in the leakage current, which is well correlated to the increase of a new capacitance peak in the C-V characteristics. Based on experimental data and bidimensional simulations, degradation is ascribed to the generation of donor traps in the GaN buffer, close to the AlGaN/GaN interface.

Here, GaN/AlxGa1-xN heterostructures with a graded AlN composition, completely lacking external p-doping, are designed and grown using metal-organic-chemical-vapour deposition (MOCVD) system to realize three-dimensional hole gas (3DHG). The existence of the 3DHG is confirmed by capacitance-voltage measurements. Based on this design, a p-doping-free InGaN/GaN light-emitting diode (LED) driven by the 3DHG is proposed and grown using MOCVD. The electroluminescence, which is attributed to the radiative recombination of injected electrons and holes in InGaN/GaN quantum wells, is observed from the fabricated p-doping-free devices. These results suggest that the 3DHG can be an alternative hole source for InGaN/GaN LEDs besides common Mg dopants. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH(3) gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN-metal interface, allowing vapor-solid-solid seeding and subsequent growth of porous GaN. Current-voltage and capacitance-voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivities. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission.

Köçkar, Hakan (Balikesir Author), In this paper we report the electrical characteristics of the Schottky diodes formed by surface polymerization of the Poly(ethylene glycol dimethanylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes on n-Si The Single Walled Carbon Nanotubes were synthesized by CVD method. The main electrical properties of the Poly(ethylene glycol dimethanylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes/n-Si have been investigated through the barrier heights, the ideality factors and the impurity density distribution, by using current-voltage and reverse bias capacitance voltage characteristics. Electrical measurements were carried out at room temperature. Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes/n-Si Schottky diode current-voltage characteristics display low reverse-bias leakage currents and average barrier heights of 0.61 +/- 0.02 eV and 0.72 +/- 0.02 eV obtained from both current-voltage and capacitance-voltage measurements at room temperature, respectively.

The Cr/n-GaAs/Cr and Ag/p-GaAs/Ag metal–semiconductor–metal (MSM) Schottky contacts have been fabricated by reactive radio frequency (RF) sputtering system. The current–voltage ðI—VÞ and capacitance–voltage ðC—VÞ characteristics of the devices have been investigated in the temperature range of 80–316 K for the back-to-back switched Schottky barrier contacts. These measurements establish that the room temperature barrier height determined from reverse branch of the current–voltage characteristics is close to the value obtained from capacitance–voltage measurements.

There is a need for a high voltage, capacitance voltage (HV, CV) measurement system for the measurement and characterization of silicon carbide (SiC) power MOSFETs. The following study discusses the circuit layout and automation software for a measurement system that can perform CV measurements for all three MOSFET capacitances, CGS, CDS, and CGD. This measurement system can perform low voltage (0–40V) and high voltage (40–5kV) measurements. Accuracy of the measurement system can be safely and effectively adjusted based on the magnitude of the MOSFET capacitance. An IRF1010N power MOSFET, a CoolMos, and a prototype SiC power MOSFET are all measured and their results are included in this study. All of the results for the IRF1010N and the CoolMos can be verified with established characteristics of power MOSFET capacitance. Results for the SiC power MOSFET prove that more testing and further development of SiC MOSFET fabrication is needed. Master of Science

Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

A description of the calculation of the cross-section for the atomic displacement σ by energetic electrons, versus penetration depth x, is given. Curves of σ(x) computed for various values of the threshold energy for displacement are given in the case of silicon. The profiles of the concentration of the defects introduced by electron irradiation of various energies in silicon is determined from capacitance-voltage measurements on gold-silicon Schottky diodes. The measurement of the defect creation rates at zero depth gives 20.5 ± 1 eV for the threshold energy.