Excellent Leakage Research Articles

High Temperature Operation of Al0.45Ga0.55N/Al0.30Ga0.70N High Electron Mobility Transistors

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that have a bandgap greater than ∼3.4 eV, beyond that of GaN and SiC, and are promising candidates for RF and power applications. Long-channel AlxGa1-xN HEMTs with x = 0.3 in the channel have been built and evaluated across the −50°C to +200°C temperature range. Room temperature drain current of 70 mA/mm, absent of gate leakage, and with a modest −1.3 V threshold voltage was measured. A very large Ion/Ioff current ratio, greater than 108 was demonstrated over the entire temperature range, indicating that off-state leakage is below the measurement limit even at 200°C. Combined with near ideal subthreshold slope factor that is just 1.3× higher than the theoretical limit across the temperature range, the excellent leakage properties are an attractive characteristic for high temperature operation.

An AlN/Al0.85Ga0.15N high electron mobility transistor

An AlN barrier high electron mobility transistor (HEMT) based on the AlN/Al0.85Ga0.15N heterostructure was grown, fabricated, and electrically characterized, thereby extending the range of Al composition and bandgap for AlGaN channel HEMTs. An etch and regrowth procedure was implemented for source and drain contact formation. A breakdown voltage of 810 V was achieved without a gate insulator or field plate. Excellent gate leakage characteristics enabled a high Ion/Ioff current ratio greater than 107 and an excellent subthreshold slope of 75 mV/decade. A large Schottky barrier height of 1.74 eV contributed to these results. The room temperature voltage-dependent 3-terminal off-state drain current was adequately modeled with Frenkel-Poole emission.

Improving the Electrical Properties of Zr-Doped Bi3.15Nd0.85Ti3O12 Thin Films by Engineering Polarization Rotation

Nd3+/Zr4+-cosubstituted bismuth titanate (BNTZx, x = 0, 0.05, 0.1, 0.3, and 0.5) thin films have been fabricated by chemical solution deposition and their polarization hysteresis loops, leakage current, and capacitance butterfly loops investigated. Results show that, at Zr content of x = 0.1, both capacitance and remanent polarization can be greatly improved. The BNTZ0.1 film also exhibits fatigue-free, excellent leakage current characteristics (I ≈ 9.44 × 10−9 A) at applied voltage of 3 V. High-quality c-axis-oriented BNTZx = 0.1 films with improved electrical properties were fabricated; this finding supports the feasibility of engineering polarization rotation in ferroelectric bismuth titanate (as suggested theoretically by Roy et al. in Appl. Phys. Lett. 102:182901, 2013).

Towards industrialisation of GaN‐on‐Si based high brightness blue LEDs

AbstractThe manufacturability of blue LED structures grown on 6‐inch Si (111) substrates is reported. The totally epi‐structure thickness is only 3.75 μm, which allows faster epitaxy process throughput and lower manufacturing costs. Well controlled strain engineering leads to a room temperature wafer bow of 0 ± 5 μm and a highly uniform photoluminescence wavelength standard deviation of 1.1 nm. XRD FWHM (002) and (102) are 380 and 390 arcsec, respectively. For a blue 1×1 mm2 vertical thin film die with silicone dome lens, the optical light output power of 563 mW at an operating voltage of 3.05 V is achieved at 350 mA. Excellent leakage current (IR) yield is achieved with over 95% of dies exhibiting IR < 0.1 μA at ‐5 V. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ferroelectric and photoelectricity properties of (Pb0.52Zr0.48)TiO3 thin films fabricated on FTO glass substrate

Perovskite-structure (Pb0.52Zr0.48)TiO3 (PZT) thin films have been fabricated on FTO(SnO2 doping F)-coated glass substrate, in which FTO were used as buffer layer and bottom electrode. The sandwich-structure Au/PZT/FTO capacitors exhibited excellent transmittancy, ferroelectric and leakage properties with the remanent polarization of about 56 μC/cm2 and leakage current density of ~10−5 A/cm2 under 5 V-bias voltage. The Au/PZT/FTO thin films changes significantly with applied DC bias field and has tunability and figure of merit of 88 % and 54 respectively under an applied field of 500 kV/cm.

Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

A Novel Load Mismatch Detection and Correction Technique for 3G/4G Load Insensitive Power Amplifier Application

This paper proposes a novel load mismatch detection and correction technique to develop a load insensitive power amplifier (PA). The presented algorithm for the technique can simply be implemented by handling load impedance as a region rather than a point. Based on the detection results, a tunable output matching network (TOMN) corrects a mismatched load and transforms it into a desired region, thereby dramatically enhancing PA performances under load mismatched condition with a minimal compromising at a matched load. The detectors and TOMN were simply implemented using a 0.18-μm silicon-on-insulator field-effect transistor, which were integrated with a 2-μm InGaP/GaAs HBT PA monolithic microwave integrated circuit into a single module. A PA module was implemented using more advanced impedance detectors having eight-phase regions, which was measured with WCDMA R'99 and 10-MHz 16QAM long-term evolution signals centered at 1.95 GHz for verification of the proposed idea. When compared to a conventional PA, excellent adjacent channel leakage ratio improvements of 12.7 and 8.3 dB, respectively, were achieved under output voltage standing-wave ratio (VSWR) of 2.5:1 for both applications. Moreover, the idea was extended for efficiency enhancement in a linearity spec-compliant impedance region, and the PA showed power-added efficiency improvements of 1.6% and 0.5%, respectively, under output VSWR of 2.5:1 for both applications.

Electrical and microstructural properties of thermally annealed Ni/Au and Ni/Pt/Au Schottky contacts on AlGaN/GaN heterostructures

High work-function metals such as Ni, Pt, and Au in the form of multilayer structures, Ni/Au and Ni/Pt/Au, have been investigated as Schottky metallizations on AlGaN/GaN heterostructures under thermal annealing. As-deposited Ni/Pt/Au had slightly higher Schottky barrier height than its Ni/Au counterpart. Schottky barrier heights for Ni/Au diodes on AlGaN/GaN increased by about 20% from 1.02 eV for as-deposited to 1.21 eV after annealing at 500 °C for 2 min. Similar trends were observed for Ni/Pt/Au Schottky diodes. Thermal stability study for these devices showed that the interposition of Pt in Ni/Au systems improved the characteristics of the Schottky diodes after short-term anneal but cause significant degradation after long-term anneal at 500 °C. Ni/Au Schottky contacts exhibited excellent leakage response under thermal annealing for long periods. Microstructural studies were carried out on Ni/Pt/Au and Ni/Au Schottky contacts to elucidate the role of the Pt interlayer in the degradation of the Ni/Pt/Au metallization under long-term thermal anneal.

A rugged 650 V SOI-based high-voltage half-bridge IGBT gate driver IC for motor drive applications

This paper proposes a rugged high-voltage N-channel insulated gate bipolar transistor (IGBT) gate driver integrated circuit. The device integrates a high-side and a low-side output stages on a single chip, which is designed specifically for motor drive applications. High-voltage level shift technology enables the high-side stage of this device to operate up to 650 V. The logic inputs are complementary metal oxide semiconductor (CMOS)/transistor transistor logic compatible down to 3.3 V. Undervoltage protection functionality with hysteresis characteristic has also been integrated to enhance the device reliability. The device is fabricated in a 1.0 μm, 650 V high-voltage bipolar CMOS double-diffused metal oxide semiconductor (BCD) on silicon-on-insulator (SOI) process. Deep trench dielectric isolation technology is employed to provide complete electrical isolation with advantages such as reduced parasitic effects, excellent noise immunity and low leakage current. Experimental results show that the isolation voltage of this device can be up to approximately 779 V at 25°C, and the leakage current is only 5 nA at 650 V, which is 15% higher and 67% lower than the conventional ones. In addition, it delivers an excellent thermal stability and needs very low quiescent current and offers a high gate driver capability which is needed to adequately drive IGBTs that have large input capacitances.

Ultrathin Oriented BiFeO3 Films from Deposition of Atomic Layers with Greatly Improved Leakage and Ferroelectric Properties

Highly (001)-oriented BiFeO3 ultrathin films of total thickness of less than 10 nm were deposited on Si(001) substrates via deposition of atomic layers (ALD) with a LaNiO3 buffer. A radio-frequency (RF)-sputtered sample of the same thickness was prepared for comparison. The ALD combined with interrupted flow and an exchange reaction between Bi and Fe precursors provides a superior method to grow ternary compounds. According to X-ray diffraction, upon deposition at a temperature of less than 550 °C, the only phase in the film was BiFeO3. Anomalous fine structure from synchrotron X-ray diffraction certified the valence bonding through the BiFeO3 (001) diffraction signal. The stoichiometric ratio of BiFeO3 obtained from X-ray photoelectron spectroscopy indicated that ALD has a proportion much improved over the RF preparation, and this is also in agreement with the results for diffraction anomalous fine structure. The use of high-resolution transmission electron and atomic force microscopes showed that the layer structure and morphology from ALD presented a satisfactory coverage, more conformal than that with the RF method. The BiFeO3 thin film deposited with ALD shows excellent leakage, improved at least 1000 times with respect to the RF preparation, making this method suitable for the fabrication of ferroelectric random-access memory devices. From the hysteresis loop, the largest remanent polarization was observed as 2Pr = 2.0 μC cm(-2).

Low temperature Ga2O3 atomic layer deposition using gallium tri-isopropoxide and water

Ga2O3 atomic layer deposition (ALD) was carried out using gallium tri-isopropoxide (GTIP) as a gallium source and H2O as an oxygen source at a low temperature (150°C). The Ga2O3 ALD films show amorphous, smooth, and transparent behavior. The growth behavior and a variety of optical, structural, and electrical properties were investigated by various measurements. The growth behavior of Ga2O3 ALD using GTIP reveals a typical ALD process, and Ga2O3 films on glass substrates show outstanding transmittance (over 90%). The Ga:O ratio was measured as 1:1.7 by the Rutherford backscattering spectrometry, and auger electron spectroscopy confirmed that there was no carbon impurity (under the detection limit). The surface morphology was investigated through an atomic force microscope analysis, and all of the films deposited at 150, 200, and 250°C showed smooth and featureless characteristics. Ga2O3 ALD thin film shows excellent leakage current (1×10−11 A at 1MV/cm) and a very suitable breakdown field (6.5–7.6MV/cm) as compared to previously reported Ga2O3 films. Also, the dielectric constant of the films is similar to that of conventional Ga2O3 films (about 9.23).

Scaled Gate Stacks for Sub-20-nm CMOS Logic Applications Through Integration of Thermal IL and ALD HfOx

The impact of gate insulator processes to achieve deeply scaled interlayer (IL)/high-k (HK) bilayer stacks for sub-20-nm CMOS on negative-bias temperature instability and positive-bias temperature instability is studied. IL scaling is done by novel low-thermal-budget rapid-thermal-process-based ultrathin IL and monolayer IL. Innovative IL top surface treatment enables integration of IL and atomic-layer-deposition-based hafnium oxide HK without vacuum break. Fully integrated stacks show scaling of equivalent oxide thickness down to ~6Å, with excellent gate leakage, mobility, and world-class BTI. The mechanism responsible for improved BTI is discussed.

Controlled deposition of new organic ultrathin film as a gate dielectric layer for advanced flexible capacitor devices

This letter describes a new organic (1-bromoadamantane) ultrathin film as gate dielectric, which was successfully deposited by sol–gel spin-coating process on a flexible polyimide substrate at room temperature. The metal–insulator-metal (MIM) device with organic (1-bromoadamantane) ultrathin (10 nm) film as gate dielectric layer operated at gate voltage of 5.0 V, showing a low leakage current density (5.63 × 10−10 A cm−2 at 5 V) and good capacitance (2.01 fF μm−2 at 1 MHz). The chemical structure of the 1-bromoadamantane layer was investigated by Fourier transform infrared spectrometer. The excellent leakage current density and better capacitance, probably due to the presence of polar, non-polar, low-polar groups, and bromine atoms in ultrathin film. Practical properties of the film in MIM capacitor such as dielectric constant as well as bending result of leakage current density and breakdown voltage have been better related to such fundamental adhesion nature over flexible substrate. This permits estimation of the properties of new dielectric in thin film form and short lists of the best materials for low loss and good capacitance flexible capacitors could be drawn up in future.

Understanding using the Haling Power Depletion (HPD) as a guide for designing PWR cores

The Pennsylvania State University (PSU) is using the university version of the Studsvik Scandpower Code System (CMS) for research and education purposes. Preparations have been made to incorporate the CMS codes into the PSU Nuclear Engineering graduate class “Nuclear Fuel Management” course. The information presented in this paper has been developed during two phases of preparation of the material for the course. In the first phase, the Haling Power Depletion (HPD) was presented in the course for the first time. The HPD method has been criticized as not valid by many in the field even though it has been successfully applied at PSU for the past 20years. It was noticed during the first phase that the radial power distribution (RPD) for low leakage cores during depletion remained similar to that of the HPD during most of the cycle and have close maximum normalized power values (NPmax’s) and cycle lengths. Thus, the Haling Power Depletion (HPD) may be used as a guide for conveniently designing mainly low leakage PWR cores because the HPD and actual core are similar. Studies were then made to better understand the HPD. Many different core configurations can be computed quickly with the HPD without using Burnable Poisons (BPs) to produce several excellent low leakage core configurations that are viable for power production. The first phase covered the solution to design a low leakage core for a cycle length of 16GWD/MTU. Once the HPD core configuration is chosen as a potential core, it is followed by establishing a BP design to prevent violating any of the safety constraints during depletion. The problem to design a core for a cycle length of 18GWD/MTU was not covered in the first phase. However, this cycle length has now been found to be beyond the scope of the course. Consequently, the cycle length is now assigned to be 17GWD/MTU and the solution to this problem is covered in the second phase. Adding more BPs in this core for a solution than in phase one was more difficult to design. Consequently, techniques using the HPD results have been developed to help guide efficiently the placing of BPs in the core for a good solution. In this paper, the results of both phases of preparation for the course are presented.

Bi1.5Zn1.0Nb1.5O7 thin films deposited at low temperature and post-annealed for crystallization

Near-stoichiometric Bi1.5Zn1.0Nb1.5O7 (BZN) thin films were prepared on Pt/TiO2/SiO2/Si (100) substrates at 400 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The as-deposited BZN thin films were post-annealed at 700 °C for 30 min in situ vacuum chamber (in situ) and in oxygen ambient oven (ex situ). The crystallinity, microstructure and electrical properties of BZN thin films were investigated. The X-ray diffractometer results indicate that BZN thin films deposited at 400 °C are amorphous in nature and the post-annealed thin films exhibit a cubic pyrochlore structure. The as-deposited BZN thin films show permittivity of 68 and loss tangent of 0.0011 at 10 kHz, respectively. After a post-annealing at 700 °C for 30 min, the dielectric properties of thin films are significantly improved. Permittivity and loss tangent of the in situ annealed films are 127 and 0.005 at 10 kHz, respectively. And the films post-annealed in O2 oven show the largest permittivity of 170 and tangent of 0.006. The improved dielectric properties can attribute to the crystallization of thin films. BZN thin films deposited at low temperature and crystallized at high temperature show the dielectric tunability without an electric breakdown to the maximum measurement bias voltage. And BZN thin films also show the excellent leakage current properties.

Preparation and Characterization of Ba(ZrxTi1-x)O3Thin Films Using Reactive Sputtering Method

Ba(ZrxTi1-x)O3 (BZT) thin films with different Zr contents were deposited on (100) MgO and (100) Pt/(100) MgO substrates by RF-magnetron reactive sputtering using metal targets. The BZT (0 < x < 0.89) thin films had a single perovskite phase with only (001)/(100) orientation. In all cases, the ratio of Ba/Ti was stoichiometric according to X-ray fluorescence spectrometry (WDX) measurement. Atomic force microscopy (AFM) study proved that BZT films possess a dense microstructure without cracks or voids. The grain size was found to decrease with increasing of Zr content. The effect of Zr content on the dielectric constant and leakage current was studied. BZT thin films showed ferroelectric-to-paraelectric properties with increasing Zr content and excellent leakage properties according to measurements of electrical properties. These results indicated that we succeeded in depositing high-quality and low-sputter-damage BZT thin films by reactive sputtering using metal targets.

Preparation and Characterization of Ba(ZrxTi1-x)O3 Thin Films Using Reactive Sputtering Method

Ba(ZrxTi1-x)O3 (BZT) thin films with different Zr contents were deposited on (100) MgO and (100) Pt/(100) MgO substrates by RF-magnetron reactive sputtering using metal targets. The BZT (0 < x < 0.89) thin films had a single perovskite phase with only (001)/(100) orientation. In all cases, the ratio of Ba/Ti was stoichiometric according to X-ray fluorescence spectrometry (WDX) measurement. Atomic force microscopy (AFM) study proved that BZT films possess a dense microstructure without cracks or voids. The grain size was found to decrease with increasing of Zr content. The effect of Zr content on the dielectric constant and leakage current was studied. BZT thin films showed ferroelectric-to-paraelectric properties with increasing Zr content and excellent leakage properties according to measurements of electrical properties. These results indicated that we succeeded in depositing high-quality and low-sputter-damage BZT thin films by reactive sputtering using metal targets.

Effects of SrTiO3 buffer layer on structural and electrical properties of Bi3.15Nd0.85Ti3O12 thin films prepared by a chemical method

Ferroelectric Bi3.15Nd0.85Ti3O12 (BNT) thin films have been grown on Pt/Ti/SiO2/Si substrates at 750°C by a chemical solution deposition method using SrTiO3 (STO) as a buffer layer. The influence of STO buffer layer on the phase and microstructure of BNT thin films was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical properties were investigated both for BNT thin films with and without STO buffer layer. The results showed that STO buffer layer strongly influenced the microstructure and electric properties of BNT thin films. BNT ferroelectric thin films with STO buffer layer exhibited the good crystallization behavior, the enhanced fatigue characteristics and excellent leakage current properties. This indicates that the introduction of the STO buffer layer prevents the interfacial diffusion and charge injection between BNT thin films and the substrate effectively and improves the interface quality.

Improved Characteristics of HKMG MOS Capacitor with Different Ultrathin Interface Layers

In order to improve the HKMG interface states density and electrical characteristics, four different interface layers have been studied in this paper. They are 7Aå thickness of SiO2 produced by rapid thermal annealing process at 1000°C, 4Aå thickness of SiO2 produced by rapid thermal annealing process at 700°C, 10Aå thickness of silicon nitride produced by LPCVD process at 620°C, and 20Aå thickness of SiO2 produced by traditional horizontal furnace process at 830°C. It was found that there were two samples, the interface layers of 7Aå SiO2 and 10Aå silicon nitride, having excellent interface state density (1.5~1.7×1011cm-2ev-1) and gate leakage (3.1~3.5×10-7A). Considering the thinner equivalent oxide thickness (Eot), we choose 10Aå silicon nitride as the best one

Preparation of Activated Carbons for Electrochemical Capacitors by Microwave Heating

Activated carbons (ACs) were prepared from lignite by microwave heating with KOH as activation agent, the effects of the weight ratio of KOH to coal and microwave heating time on the pore structure of ACs were investigated by N2 adsorption. The electrochemical characteristics of electrochemical capacitors (ECs) with ACs as electrodes in 3mol/L KOH electrolyte were evaluated by galvanostatic charge/discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the BET specific surface area and total pore volume of ACs (denoted as AC-R3) can reach 2097m2/g and 1.19cm3/g respectively when the weight ratio of KOH to coal is 3:1 and the microwave heating time is 10 min. The ECs with AC-R3 as electrodes presents a high specific capacitance of 335F/g at a low current density of 50mA/g and still remains 288F/g even at a high current density of 5A/g, it has excellent cycling stability and low leakage current, and the residual specific capacitance is as high as 93.6% after 1000 cycles under the current density of 2.5A/g. The results have demonstrated that the microwave heating with KOH activation is an efficient approach to prepare ACs with high performance for ECs. Keywords: Activated Carbons; Microwave Heating; Electrochemical Capacitors; Electrochemical Characteristics