Study on the Characteristics of SOI DTMOS with Reverse Schottky Barriers

Silicon-on-insulator dynamic threshold voltage MOSFETs with TiSi2/pSi as reverse Schottky barriers （RSB） are presented. With this RSB scheme,DTMOS can operate beyond 0.7V, thus overcoming the drawback of DTMOS with the gate and body connected. The experimental results demonstrate that the threshold voltage in DT mode with an RSB is reduced by about 200mV at room temperature. SOI MOSFETs in DT mode with an RSB have advantages such as excellent subthreshold slope and high drivability over those under normal mode operation. The breakdown characteristics of SOI MOSFETs in the off-state are compared for the DT mode with RSB, floating body mode, normal mode.

Effect of annealing on the electrical performance of N-polarity GaN Schottky barrier diodes

A nitrogen-polarity(N-polarity)GaN-based high electron mobility transistor(HEMT)shows great potential for high-fre-quency solid-state power amplifier applications because its two-dimensional electron gas(2DEG)density and mobility are mini-mally affected by device scaling.However,the Schottky barrier height(SBH)of N-polarity GaN is low.This leads to a large gate leakage in N-polarity GaN-based HEMTs.In this work,we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes(SBDs)with Ni/Au electrodes.Our results show that the annealing time and tem-perature have a large influence on the electrical properties of N-polarity GaN SBDs.Compared to the N-polarity SBD without annealing,the SBH and rectification ratio at±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700,respec-tively,and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process.Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the inter-face state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emis-sion from the trap state at low reverse bias.

Improvement of Ga_(2)O_(3)vertical Schottky barrier diode by constructing NiO/Ga_(2)O_(3)heterojunction

The high critical electric field strength of Ga_(2)O_(3)enables higher operating voltages and reduced switching losses in power electronic devices.Suitable Schottky metals and epitaxial films are essential for further enhancing device performance.In this work,the fabrication of vertical Ga_(2)O_(3)barrier diodes with three different barrier metals was carried out on an n--Ga_(2)O_(3)homogeneous epitaxial film deposited on an n+-β-Ga_(2)O_(3)substrate by metal-organic chemical vapor deposition,excluding the use of edge terminals.The ideal factor,barrier height,specific on-resistance,and breakdown voltage characteristics of all devices were investigated at room temperature.In addition,the vertical Ga_(2)O_(3)barrier diodes achieve a higher breakdown volt-age and exhibit a reverse leakage as low as 4.82×10^(-8)A/cm^(2)by constructing a NiO/Ga_(2)O_(3)heterojunction.Therefore,Ga_(2)O_(3)power detailed investigations into Schottky barrier metal and NiO/Ga_(2)O_(3)heterojunction of Ga_(2)O_(3)homogeneous epitaxial films are of great research potential in high-efficiency,high-power,and high-reliability applications.

High frequency doubling efficiency THz GaAs Schottky barrier diode based on inverted trapezoidal epitaxial cross-section structure

A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper.Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer,by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified.The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area.Compared with the normal structure,the grading coefficient M increases from 0.47 to 0.52,and the capacitance modulation ratio(C^(max)/C_(min))increases from 6.70 to 7.61.The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge.A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35%compared to that 30%of a normal SBD.

High performance trench diamond junction barrier Schottky diode with a sidewall-enhanced structure

The trench diamond junction barrier Schottky(JBS)diode with a sidewall enhanced structure is designed by Silvaco simulation.Comparing with the conventional trench JBS diode,Schottky contact areas are introduced on the sidewall of the trench beside the top cathode.The sidewall Schottky contact weakens the junction field-effect transistor effect between the trenches to realize a low on-resistance and a high Baliga's figure of merit(FOM)value.In addition,the existence of the n-type diamond helps to suppress the electric field crowding effect and enhance the reverse breakdown voltage.With the optimal parameters of device structure,a high Baliga's FOM value of 2.28 GW/cm^(2) is designed.Therefore,the proposed sidewall-enhanced trench JBS diode is a promising component for the applications in diamond power electronics.

Spin injection into heavily-doped n-GaN via Schottky barrier

Spin injection and detection in bulk GaN were investigated by performing magnetotransport measurements at low temperatures.A non-local four-terminal lateral spin valve device was fabricated with Co/GaN Schottky contacts.The spin injection efficiency of 21%was achieved at 1.7 K.It was confirmed that the thin Schottky barrier formed between the heavily ndoped GaN and Co was conducive to the direct spin tunneling,by reducing the spin scattering relaxation through the interface states.

β-Ga_(2)O_(3) junction barrier Schottky diode with NiO p-well floating field rings

Recently,β-Ga_(2)O_(3),an ultra-wide bandgap semiconductor,has shown great potential to be used in power devices blessed with its unique material properties.For instance,the measured average critical field of the vertical Schottky barrier diode(SBD)based onβ-Ga_(2)O_(3) has reached 5.45 MV/cm,and no device in any material has measured a greater before.However,the high electric field of theβ-Ga_(2)O_(3) SBD makes it challenging to manage the electric field distribution and leakage current.Here,we showβ-Ga_(2)O_(3) junction barrier Schottky diode with NiO p-well floating field rings(FFRs).For the central anode,we filled a circular trench array with NiO to reduce the surface field under the Schottky contact between them to reduce the leakage current of the device.For the anode edge,experimental results have demonstrated that the produced NiO/β-Ga_(2)O_(3) heterojunction FFRs enable the spreading of the depletion region,thereby mitigating the crowding effect of electric fields at the anode edge.Additionally,simulation results indicated that the p-NiO field plate structure designed at the edges of the rings and central anode can further reduce the electric field.This work verified the feasibility of the heterojunction FFRs inβ-Ga_(2)O_(3) devices based on the experimental findings and provided ideas for managing the electric field ofβ-Ga_(2)O_(3) SBD.

Design optimization of high breakdown voltage vertical GaN junction barrier Schottky diode with high-K/low-K compound dielectric structure

A vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage(BV).There is a discontinuity of the electric field at the interface of high-K and low-K layers due to the different dielectric constants of high-K and low-K dielectric layers.A new electric field peak is introduced in the n-type drift region of junction barrier Schottky diode(JBS),so the distribution of electric field in JBS becomes more uniform.At the same time,the effect of electric-power line concentration at the p-n junction interface is suppressed due to the effects of the high-K dielectric layer and an enhancement of breakdown voltage can be achieved.Numerical simulations demonstrate that GaN JBS with a specific on-resistance(R_(on,sp)) of 2.07 mΩ·cm^(2) and a BV of 4171 V which is 167% higher than the breakdown voltage of the common structure,resulting in a high figure-of-merit(FOM) of 8.6 GW/cm^(2),and a low turn-on voltage of 0.6 V.

An Analytical Model of Drain Current for Ultra-Thin Body and Double-Gate Schottky Source/Drain MOSFETs Accounting for Quantum Effects

A compact drain current including the variation of barrier heights and carrier quantization in ultrathin-body and double-gate Schottky barrier MOSFETs （UTBDG SBFETs） is developed. In this model, Schrodinger＇s equation is solved using the triangular potential well approximation. The carrier density thus obtained is included in the space charge density to obtain quantum carrier confinement effects in the modeling of thin-body devices. Due to the quantum effects, the first subband is higher than the conduction band edge, which is equivalent to the band gap widening. Thus, the barrier heights at the source and drain increase and the carrier concentration decreases as the drain current decreases. The drawback of the existing models,which cannot present an accurate prediction of the drain current because they mainly consider the effects of Schottky barrier lowering （SBL） due to image forces,is eliminated. Our research results suggest that for small nonnegative Schottky barrier （SB） heights,even for zero barrier height, the tunneling current also plays a role in the total on-state currents. Verification of the present model was carried out by the device numerical simulator-Silvaco and showed good agreement.

Ti/4H-SiC Schottky Barrier Diodes with Field Plate and B^+ Implantation Edge Termination Technology

This paper describes the fabrication and electrical characteristics of Ti/4H-SiC Schottky barrier diodes （SBDs）. The ideality factor n = 1.08 and effective Schottky barrier heightφ= 1.05eV of the SBDs were measured with the method of forward current density-voltage （J-V）. A low reverse leakage current below 5.96 ×10^-3A/cm^2 at a bias voltage of - 1. 1kV was obtained. By using B^＋ implantation,an amorphous layer as the edge termination was formed. We used the PECVD SiO2 as the field plate dielectric. The SBDs have an on-state current density of 430A/cm^2 at a forward voltage drop of about 4V. The specific on-resistance Ro, was found to be 6. 77mΩ2 · cm^2 .

Schottky Barrier Characteristics of Polycrystalline and Epitaxial CoSi_2/n-Si(111) Contacts Formed by Solid State Reaction

Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The CoSi 2/Si Schottky contacts are measured with the current-voltage and capacitance-voltage (I-V/C-V) techniques within the range of temperature from 90K to room temperature.The measured I-V characteristics have been analyzed with a model based on the inhomogeneity in Schottky barrier height,i.e.,at high temperatures (≥～200K) or low temperatures but with a large bias,the I-V curves can be described by using the thermionic emission theory with a Gaussian distributed barrier height over the whole junction,while at low temperatures and with a small bias,the current is dominated by some small patches with low barrier height.It results in a plateau-like section in the low temperature I-V curves around 10 -7 A.At room temperature,the barrier height of polycrystalline CoSi 2/Si deduced from the I-V curve is about 0 57eV.For epitaxial CoSi 2,the barrier height depends on its final annealing temperature and increases from 0 54eV to 0 60eV with the annealing temperature increasing from 700℃ to 900℃.

High-Voltage Ti /6H-SiC Schottky Barrier Diodes

The fabrication and electrical characterization of Scho tt ky barrier diodes (SBD) on 6H-SiC,via thermal evaporation of Ni are reported.Th e Schottky barrier diodes are fabricated during the 6H-SiC epilayers grow n by using chemical vapor deposition on commercially available single-crystal 6 H-SiC wafers.The I-V characteristics of these diodes exhibit a sharp break down,with the breakdown voltage of 450V at room temperature.The diodes are demon strated to be of a low reverse leakage current of 5×10 -4 A·cm -2 at the bias voltage of -200V.The ideal factor and barrier height are 1 09 and 1 24-1 26eV,respectively.

High-Responsivity ZnS Schottky Barrier Photodiode Array for Ultraviolet Imaging

A different approach,using the molecular beam epitaxy (MBE)-grown ZnS-based Schottky photodiode technology,is applied to fabricate an 8×8 photodiode array.The micro-processing procedures of this photodiode array including standard photolithography,a number of metallisation,wet-chemical etching and SiO_2 deposition for insulation are developed.The detector is characterized to have a cutoff wavelength at 340 nm and the photo-responsivity measurements on the pixels result an ultraviolet (UV) response as high as 0.15 A/W,corresponding to an external quantum efficiency of 55% in the visible-blind spectral ranging from 400 down to 250nm.Imaging tests indicate that this array is able to capture the intensity profile of a given UV light source with reasonably good capability.

A generalized Norde plot for reverse biased Schottky contacts

When a metal makes intimate contact with a semiconductor material, a Schottky barrier may be created. The Schottky contact has many important applications in the integrated circuit （IC） electronics field. The parameters of such contacts can be determined from their current-voltage （I-V） characteristics. The literature contains many proposals for extracting the contact parameters using graphical methods. However, such methods are generally applicable only to contacts with a forward bias, whereas many Schottky contacts actually operate un- der a reverse bias. Accordingly, the present study proposed a generalized reverse current-voltage （I-V） plot which enables the series resis- tance, barrier height, and ideality factor of a reverse biased Schottky contact to be extracted from a single set of I-V measurements. A theo- retical derivation of the proposed approach was presented and a series of validation tests were then performed. The results show that the pro- posed method is capable of extracting reliable estimates of the contact parameters even in the presence of experimental noise.

Threshold Voltage Model of a Double-Gate MOSFET with Schottky Source and Drain

A quasi two-dimensional （2D） analytical model of a double-gate （DG） MOSFET with Schottky source/drain is developed based on the Poisson equation.The 2D potential distribution in the channel is calculated.An expression for threshold voltage for a short-channel DG MOSFET with Schottky S/D is also presented by defining the turn-on condition.The results of the model are verified by the numerical simulator DESSIS-ISE.

Analysis and simulation of a 4H-SiC semi-superjunction Schottky barrier diode for softer reverse-recovery

In this paper, a 4H-SiC semi-superjunction （S J） Schottky barrier diode is analysed and simulated. The semi-SJ structure has an optimized design and a specific on-resistance lower than that of conventional SJ structures, which can be achieved without increasing the process difficulty. The simulation results show that the specific on-resistance and the softness factor depend on the aspect and thickness ratios, and that by using the semi-SJ structure, specific on-resistance can be reduced without decreasing the softness factor. It is observed that a trade-off exists between the specific on-resistance and the softness of the diode.

Edge termination study and fabrication of a 4H-SiC junction barrier Schottky diode

The 4H-SiC junction barrier Schottky （JBS） diodes terminated by field guard rings and offset field plate are designed, fabricated and characterized. It is shown experimentally that a 3-μm P-type implantation window spacing gives an optimum trade-off between forward drop voltage and leakage current density for these diodes, yielding a specific on-resistance of 8.3 mΩ-cm2. A JBS diode with a turn-on voltage of 0.65 V and a reverse current density less than 1 A/cm2 under 500 V is fabricated, and the reverse recovery time is tested to be 80 ns, and the peak reverse current is 28.1 mA. Temperature-dependent characteristics are also studied in a temperature range of 75 °C-200 °C. The diode shows a stable Schottky barrier height of up to 200°C and a stable operation under a continuous forward current of 100 A/cm2.

Study and optimal simulation of 4H-SiC floating junction Schottky barrier diodes' structures and electric properties

This paper stuides the structures of 4H SiC floating junction Schottky barrier diodes. Some structure parameters of devices are optimized with commercial simulator based on forward and reverse electrical characteristics. Compared with conventional power Schottky barrier diodes, the devices are featured by highly doped drift region and embedded floating junction layers, which can ensure high breakdown voltage while keeping lower specific on-state resistance, and solve the contradiction between forward voltage drop and breakdown voltage. The simulation results show that with optimized structure parameter, the breakdown voltage can reach 4.36 kV and the specific on-resistance is 5.8 mΩ.cm2 when the Baliga figure of merit value of 13.1 GW/cm2 is achieved.

A simulation study of field plate termination in Ga2O3 Schottky barrier diodes

In this work, the field plate termination is studied for Ga2O3Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated.It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO2, Al2O3, and HfO2. As the thickness increases, the maximum electric field intensity decreases in SiO2and Al2O3, but increases in HfO2.Furthermore, it is found that SiO2and HfO2are suitable for the 600 V rate Ga2O3SBD, and Al2O3is suitable for both600 V and 1200 V rate Ga2O3SBD. In addition, the comparison of Ga2O3SBDs between the SiC and GaN counterpart reveals that for Ga2O3, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.

Improvements in reverse breakdown characteristics of THz GaAs Schottky barrier varactor based on metal-brim structure

The excellent reverse breakdown characteristics of Schottky barrier varactor(SBV)are crucially required for the application of high power and high efficiency multipliers.The SBV with a novel Schottky structure named metal-brim is fabricated and systemically evaluated.Compared with normal structure,the reverse breakdown voltage of the new type SBV improves from-7.31 V to-8.75 V.The simulation of the Schottky metal-brim SBV is also proposed.Three factors,namely distribution of leakage current,the electric field,and the area of space charge region are mostly concerned to explain the physical mechanism.Schottky metal-brim structure is a promising approach to improve the reverse breakdown voltage and reduce leakage current by eliminating the accumulation of charge at Schottky electrode edge.