Dependence Of Leakage Current Research Articles

Origin of exponentially large increase in the leakage current in alumina films depending on the ALD synthesis temperature

Amorphous aluminum oxide a-Al2O3 deposited by atomic layer deposition (ALD) is widely used in nonvolatile memory devices. In this paper, the leakage current dependence on the ALD synthesis temperature is investigated by six charge transport models: Schottky effect, thermally assisted tunneling at a contact, Frenkel effect, Hill-Adachi model of overlapping Coulomb potentials, Makram-Ebeid and Lannoo multiphonon isolated trap ionization model, and Nasyrov–Gritsenko model of phonon-assisted tunneling between neighboring traps. It is shown that the leakage current exponentially increases with the ALD synthesis temperature, which is related to the increase in trap concentration.

Voltage and temperature dependence of reverse leakage current of lattice-matched InAlN/GaN heterostructure Schottky contact

In this paper, the temperature-dependent current-voltage (<i>T-</i><i>I-</i><i>V</i>) characteristics of lattice-matched InAlN/GaN heterostructure Schottky contact in a reverse direction are measured, and the voltage dependence and temperature dependence of the leakage current are studied. The obtained results are as follows.1) The reverse current is a strong function of voltage and temperature, and the saturation current is much larger than the theoretical value, which cannot be explained by the classical thermionic emission (TE) model. 2) In the low-bias region, the <inline-formula><tex-math id="Z-20210326091652-1">\begin{document}$ \ln(I/E)\text{-}E^{1/2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20201355_Z-20210326091652-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20201355_Z-20210326091652-1.png"/></alternatives></inline-formula> data points obey a good linear relationship, whose current slope and corresponding activation energy are close to the values predicted by the Frenkel-Poole (FP) model, indicating the dominant role of the FP emission mechanism. 3) In the high-bias region, the <inline-formula><tex-math id="Z-20210326091730-1">\begin{document}$ \ln(I/E^2)\text{-}E^{-1} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20201355_Z-20210326091730-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20201355_Z-20210326091730-1.png"/></alternatives></inline-formula>data points also follow a linear dependence, but the current slope is a weak function of temperature, indicating that the Fowler-Nordheim tunneling mechanism should be mainly responsible for the leakage current. 4) The current barrier height is extracted to be about 0.60 eV, which is much lower than the value of 2.91 eV obtained from the TE model, confirming the primary leakage path of the conductive dislocations, where the localized barrier is significantly reduced due to the ionization of shallow donor-like traps.

AlGaN/GaN HEMT channel temperature determination utilizing external heater

An improved method of average channel temperature and channel temperature profile determination is introduced in this paper applied to AlGaN/GaN HEMT using quasi-static I–V characterization and external heater. Particular HEMT resistances and threshold voltage were experimentally determined at different ambient temperatures from TLM measurements, HEMT output and transfer I–V characteristics. Negligible pinch-off area and leakage current dependence on drain voltage allows to obtain average temperature ∼77 °C for dissipated power 1.5 W using simple recurrent differential calculations. The HEMT channel temperature profile exhibiting maximum peripheral temperature ∼130 °C for dissipated power 1.5 W was simulated and verified utilizing the device electrical parameters variation.

High-temperature performance of gallium-nitride-based pin alpha-particle detectors grown on sapphire substrates

The temperature-dependent radiation-detection performance of an alpha-particle detector that was based on a gallium-nitride (GaN)-based pin structure was studied from 290 K to 450 K. Current–voltage–temperature measurements (I–V–T) of the reverse bias show the exponential dependence of leakage currents on the voltage and temperature. The current transport mechanism of the GaN-based pin diode from the reverse bias I–V fitting was analyzed. The temperature-dependent pulse-height spectra of the detectors were studied using an 241 Am alpha-particle source at a reverse bias of 10 V, and the peak positions shifted from 534 keV at 290 K to 490 keV at 450 K. The variation of full width at half maximum (FWHM) from 282 keV at 290 K to 292 keV at 450 K is almost negligible. The GaN-based pin detectors are highly promising for high-temperature environments up to 450 K.

Fluctuations of Current in Polycrystalline Ferroelectric Ceramics

Experimental data on fluctuations of leakage currents over time in samples of polycrystalline ferroelectric ceramics (SBPZT-1, ceramics based on sodium bismuth lead zirconate–titanate) upon the application of a constant electric field are considered. Variations in the type of leakage current dependence on time with an increase in electric field strength on samples with different values of the loss-angle tangent are determined. Exponential decay is accompanied by random jumps, i.e., variations in the values of the leakage current.

Strong composition dependence of resistive switching in Ba1-xSrxTiO3 thin films on semiconducting substrates and its thermodynamic analysis

In this work, we report on the variability of the Schottky effect in solution processed Ba1-xSrxTiO3 films (BST, x = 0, 0.5) grown on 0.5% Nb doped SrTiO3 substrates with top Pt electrodes (NSTO/BST/Pt). The films display leakage currents accompanied by varying degrees of hystereses in the current-voltage measurements. The magnitude of the leakage and hystereses depend on the Sr content. We focus on the current-voltage (I-V) behavior of our samples in the light of thermodynamic theory of ferroelectrics coupled with equations of semiconductors. Our calculations allowed us to unambigously determine the electronic character of the defects and related band bending effects in our samples. The extent of asymmetry and the hystereses in the I-V curves for x = 0 and 0.5 are shown to be controlled by the polarization in qualitative agreement with our calculations. Amplitude of the ferroelectric polarization, which is a function of composition here, has a strong impact on leakage currents in forward bias while this effect is much weaker under negative bias. The latter occurs as polarization pointing away from the NSTO semiconducting substrate causes depletion of carriers at the NSTO side of the NSTO/BST interface, increasing resistance to current flow through the stack. Such an occurence also increases the energy gap between the Fermi level and the conduction bands of the films, thereby reducing the bulk conduction through the film as well. The dependence of leakage currents on polarization direction points out to the possibility of a non-destructive read-out route in ferroelectric films much thicker than tunnel junctions.

Facet dependence of leakage current and carrier concentration in m-plane GaN Schottky barrier diode fabricated with MOVPE

In this study, GaN m-plane Schottky barrier diodes fabricated with a metalorganic vapor-phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse-biased condition was observed. We showed that the leakage-current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m-plane devices. (a) four-faceted hillocks on m-plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m-plane GaN Schottky barrier diode.

Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

We perform transport measurements on double quantum dots defined in Ge/Si core/shell nanowires and focus on Pauli spin blockade in the regime where tens of holes occupy each dot. We identify spin blockade through the magnetic field dependence of leakage current. We find both a dip and a peak in the leakage current at zero field. We analyze this behavior in terms of the quantum dot parameters such as coupling to the leads, interdot tunnel coupling as well as spin-orbit interaction. We find a lower bound for spin-orbit interaction with $l_{\rm so}=500$ nm. We also extract large and anisotropic effective Land$\rm \acute{e}$ g-factors, with larger g-factors in the direction perpendicular to the nanowire axis in agreement with previous studies and experiments but with larger values reported here.

LTCC Breakdown Voltage Investigation

Abstract High voltage properties of the LTCC (Low Temperature Co-Fired Ceramics) cofired ceramic tape are presented. Chauvin Arnoux C.A. 6555 insulation tester is used to measure the leakage current and the resistance. Measurement is possible up to 15 kV. The DuPont 951 test structures are manufactured. The electrodes are fabricated of Ag (DP 6142) and PdAg (DP 6146) pastes. The leakage current dependence upon the temperature up to 320°C is measured. The ceramics properties depend on the temperature, especially beyond 200°C. Moreover, the current characteristics as a function of electrical field are presented and the breakdown voltage is determined.

Annealing Mechanism and Effect of Microwave Plasma Assisted Annealing on Properties of Sputtered Pb(Zr0.52Ti0.48)O3 Thin Films.

To solve some problems existing in PZT films, such as: large residual stresses, interface diffusion, and lead loss, etc., which were caused by high post-annealing temperatures, and to obtain thin films with high-preferred orientation and uniform size grain and dense microstructure, different technological conditions of microwave plasma assisted post-annealing had been pilot studied. X-ray diffraction was used to analyze the crystal structures of the films. Transmission electronic microscope was used to analyze the surface and the interface morphology of the films. Ferroelectric properties were showed by measuring the remnant polarization and the leakage current dependence of electric field. The results indicated that it was good for reducing lead loss and annealing temperature of PZT films by microwave plasma assisted annealing. Ferroelectric properties of the film could also be enhanced by this pilot annealing method.

Novel Palladium Germanide Schottky Contact for High Performance Schottky Barrier Ge MOSFETs and Characterization of Its Leakage Current Mechanism

The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

Recent advances in processing and characterization of edgeless detectors

During past five years VTT has actively developed edgeless detector fabrication process. The straightforward and high yield process relies on ion-implantation to activate the edges of the detector. A recent fabrication process was performed at VTT to provide p-on-n edgeless detectors. The layout contained DC- and AC-coupled strip detector and pixel detectors for Medipix/Timepix readouts. The fabricated detector thicknesses were 50, 100 and 150 μm. Electrical characterization was done for 5 × 5 mm2 edgeless diodes on wafer level. All measured electrical parameters showed a dramatic dependence on the diode thickness. Leakage current was measured below 10 nA/cm2 at full depletion. Calculation using a theoretical approximation indicates the diode surface generation current of less than 300 pA. The breakdown voltages were measured to be above 140 V and increased as a function of diode thickness. Reverse bias of 10 V is enough to fully deplete designed edgeless diodes. Leakage current dependence of temperature was investigated for both p-on-n and previous n-on-n edgeless detectors and results show that the leakage current doubles for every 8.5 degree Celsius rise in temperature. TCAD device simulations reveal that breakdown occurs at the lateral p-n junction where the electric field reaches its highest value. Thick edgeless diodes have wider bulk space that allows electric potential to drop and causes smaller curvature of the equipotential lines. This releases the accumulation of electric field at the corner of anode and increases the breakdown voltage. A good match of the simulated and the measured capacitance-voltage curves enables identification of proper parameters used in the simulation.

Analyses of the Leakage Current Characteristics of Lead Lanthanum Titanate-Cobalt Iron Oxide Multiferroic Composite Thin Film

We have investigated the leakage current characteristics of polycrystalline lead lanthanum titanate (PLT) - cobalt iron oxide (CFO) composite multiferroic thin films. The dc conductivity is found to increase monotonically with the increase of CFO volume contents. From the measurement of both field and temperature dependence of leakage current, Schottky emission is found to be the dominant current conduction mechanism in these composite films. The frequency dependence of ac conductivity obeys Jonscher power law. Probing the temperature dependence of ac conductivity the plausible ac conduction mechanism in these films is discussed.

Effect of different annealing methods on ferroelectric properties of 0.95Pb(Sc 0.5Ta 0.5)O 3–0.05PbTiO 3 thin films

0.95Pb(Sc 0.5Ta 0.5)O 3–0.05PbTiO 3 thin films were prepared on LaNiO 3/SiO 2/Si substrate by radio frequency magnetron sputtering, and the films were annealed subsequently with repeated many times by two approaches: normal one-step rapid thermal annealing and innovative two-steps rapid thermal annealing. X-ray diffraction demonstrates that all the films were preferred (1 0 0) oriented and an appropriate repeat of annealing process can enhance perovskite phase of the films. Scanning electron microscopy suggests that the films treated by two-steps rapid thermal annealing show crack-free, uniform size grains and dense microstructure. Measurement of remnant polarization and leakage current dependence of electric field confirms that the films treated by two-steps rapid thermal annealing exhibit better ferroelectric properties than the films treated by one-steps rapid thermal annealing. The results reveal that microstructure plays an important role in enhanced ferroelectric properties of the 0.95Pb(Sc 0.5Ta 0.5)O 3–0.05PbTiO 3 thin films.

Temperature and voltage aging effects on electrical conduction mechanism in epoxy-BaTiO 3 composite dielectric used in embedded capacitors

The electrical conduction mechanism in an embedded capacitor with epoxy-BaTiO 3 composite dielectric and Cu electrodes is investigated in this paper. Leakage current was measured across the dielectric by performing a voltage sweep from 0 to 100 V. The voltage sweep was performed at temperatures ranging from 25 °C to 125 °C. Various electrical conduction models such as Schottky, Poole–Frenkel, and ionic hopping were evaluated by comparing the functional dependence of leakage current on temperature and voltage for each mechanism which was considered. It was observed that the conduction mechanism was most consistent with Schottky emission. The contact potential barrier corresponding to Schottky emission was found to be 1.29 eV. The effect of combined temperature and voltage aging on the conduction mechanism was investigated by aging the embedded capacitor dielectric at 125 °C and 100 V for 1680 h. To investigate the difference between combined temperature and voltage aging and temperature aging alone, some capacitors were aged only by temperature at 125 °C for 1680 h. Measurements of leakage current as a function of temperature and voltage were performed at frequent intervals during the aging. It was observed that the value of leakage current did not increase during temperature and voltage aging unlike pure BaTiO 3 dielectrics.

Temperature-Aware Integrated DVFS and Power Gating for Executing Tasks With Runtime Distribution

At high-operating temperature, chip cooling is crucial due to the exponential temperature dependence of leakage current. However, traditional cooling methods, e.g., power/clock gating applied when a temperature threshold is reached, often cause excessive performance degradation. In this paper, we propose a method for delivering lower energy consumption by integrating the cooling and running in a temperature-aware manner without incurring performance penalty. In order to further reduce the energy consumption, we exploited the runtime distribution of each sub-segment of a task called “bin” in an analytical manner such that time budget for cooling in each bin is allocated in proportion to the probability of the occurrence of the bin. We apply the proposed method to two realistic software programs, H.264 decoder and ray tracing and a benchmark program, equake. The experimental results show that the proposed method yields additional 19.4%-27.2% reduction in energy consumption compared with existing methods.

Investigation of Leakage Current of AlGaN/GaN HEMTs Under Pinch-Off Condition by Electroluminescence Microscopy

Results from on-wafer electroluminescence (EL) microscopy on AlGaN/GaN high-electron-mobility transistors with leakage currents varying over four orders of magnitude are presented. In the off-state region the integrated EL intensity is proportional to the leakage current and independent of gate width for the devices under study. The slope of the integrated EL–leakage current dependence is determined by the electrical field in the source–drain direction. The influence of the GaN cap thickness is small or even negligible for higher drain bias. Stress during accelerated aging results in enhanced degradation for areas of enhanced leakage current and/or electric field values.

Band Engineering of Rutile TiO2 by Cobalt Doping in Ru/Rutile-TiO2/Ru Capacitor aiming 40-nm DRAM and Beyond

A Feasible fabrication process of Ru/rutile-Co-doped TiO2/Ru capacitor for 40-nm DRAM and beyond is developed. As-deposited Ru lower electrode is found out to crystallize Co-doped TiO2 overlayer into rutile having relative permittivity beyond 90 owing to lattice matching. Furthermore, we predicted doping of element having small ionic radius, such as Co, increase Schottky barrier, leading to decrease in leakage current. Temperature dependence of leakage current of RIR-Co-doped-TiO2 capacitor and band structure analysis with X-ray photoelectron spectroscopy shows that leakage current is determined by balancing between thermionic current and tunneling current through Schottky barrier. By doping of Co, the thermionic current decreases, whereas the tunneling current increases. With calculation using theoretical dependence of amount of doped element on leakage current, optimum percentage of Co is estimated as 0.3-0.6 % to achieve a sufficiently low leakage-current. This technology opens possibility to utilize 40-nm DRAM and beyond.

Temperature dependence of leakage currents in Ti-doped Ta2O5 films on nitrided silicon

Conduction mechanisms and electrically active defects in rf sputtered Ti doped Ta2O5 thin films have been investigated by analysing the impact of temperature on the I–V curves. The films (about 6 nm thick) were grown on silicon substrates nitrided in N2O or NH3 ambient. Two different methods of Ti incorporation were used—a surface doping, where a thin Ti layer is deposited on the top of Ta2O5, and a bulk doping, where the Ti layer is sandwiched between two layers of Ta2O5. The I–V characteristics were measured in a temperature range from 30 to 100 °C. Current is found to be governed mainly by the modified Poole–Frenkel (PF) effect, with a temperature dependent degree of compensation. Two types of trap centres involved in the PF conduction process have been identified: shallow traps located at about 0.3–0.4 eV below the conduction band edge of the dielectric, present in all doped films, and deeper centres at 0.65 eV, present only in the bulk-doped films. The origin of these trap centres is also discussed.

Evidence of carrier leakage into the L‐valley in InAs‐based quantum cascade lasers under high hydrostatic pressure

AbstractTo investigate carrier scattering processes in short wavelength InAs/AlSb quantum cascade lasers we carried out experimental and theoretical studies of the threshold current, Ith, as a function of high hydrostatic pressure and temperature. Using the calculated pressure dependence of the optical phonon scattering current, Iph, and the estimated pressure dependence of leakage current, Ileak, we show that carrier leakage from the upper laser levels into the indirect L‐valley of the conduction band in InAs quantum wells is negligible in the 3.3 μm QCLs at RT leading to their superior temperature performance. In the shorter wavelength devices emitting at 2.9 μm, this loss mechanism is more important and accounts for up to 13% of Ith at 190 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)