ISE TCAD Research Articles

Novel Si/SiC heterojunction lateral double-diffused metal oxide semiconductor field effect transistor with low specific on-resistance by super junction layer

A novel Si/SiC heterojunction lateral double-diffused metal oxide semiconductor (LDMOS) field effect transistor with the low specific on-resistance (Ron,sp) by super-junction (SJ) layer (Si/SiC SJ-LDMOS) is proposed in this paper. On the basis of using N-Buffer layer to solve substrate assisted depletion effect (SAD), breakdown point transfer terminal technology (BPT) is realized by the deep drain structure of Si/SiC heterojunction and electric field modulation is carried out, which further improves the breakdown voltage (BV) of Si/SiC SJ-LDMOS, alleviates the contradictory relationship between the BV and the Ron,sp. Through ISE TCAD simulation, the result shows that with the same drift region length of 20 μm, the BV is increased from 114 V of conventional SJ-LDMOS (Cov. SJ-LDMOS) and 270 V of SJ-LDMOS with N-Buffer layer (Buffer SJ-LDMOS) to 374 V of Si/SiC SJ-LDMOS, increased by 228% and 38%, respectively. In addition, the Ron,sp of Cov. SJ-LDMOS, Buffer SJ-LDMOS and Si/SiC SJ-LDMOS are 46.26 mΩ cm2, 26.96 mΩ cm2 and 25.85 mΩ cm2, respectively. Moreover, the figure-of-merit (FOM) of proposed Si/SiC SJ-LDMOS device is 5.411 MW/cm2, which means the Si/SiC SJ-LDMOS has a better performance to break the silicon limit. The influence of design parameters on device performance is also discussed.

Enhancement of deep violet InGaN double quantum wells laser diodes performance characteristics using superlattice last quantum barrier

Abstract The performance characteristics of InGaN double-quantum-well (DQW) laser diodes (LDs) with different last barrier structures are analyzed numerically by Integrated System Engineering Technical Computer Aided Design (ISE TCAD) software. Three different kind of structures for last quantum barrier including doped- GaN, doped- AlGaN and GaN/AlGaN superlattice last barrier are used and compared with conventional GaN last barrier in InGaN-based laser diodes. Replacing the conventional GaN last barrier with p-AlGaN increased hole flowing in the active region and consequently the radiative recombination which results in the enhancement of output power. However it caused increasing the threshold current due electron overflowing. For solving this problem, the last barrier structure altered with GaN/AlGaN superlattice. The simulation indicates that the electrical and optical characteristics of LDs with the superlattice last barrier, like output power, differential quantum efficiency (DQE) and slope efficiency, has significantly improved, besides the threshold current decreased. The enhancement is mainly attributed to the improvement of hole injection and the blocking electron overflowing which are caused by the reduction of polarization charges at the interface between the barrier and well, and electron blocking layer (EBL).

Breakdown point transfer theory for Si/SiC heterojunction LDMOS with deep drain region

Abstract Heterojunction terminal technology, especially Si/SiC heterojunction, has been widely used in the power semiconductor device. Si/SiC heterojunction LDMOS combines the advantages of Si and SiC while the breakdown point is transferred due to employing the deep drain region structure to improve the BV of the device. Based on the existing research, a new theory about breakdown point transfer terminal technology is proposed for silicon on silicon carbide lateral double-diffused metal oxide semiconductor field effect transistor with deep drain region based on the electric field modulation in this paper for the first time. A concise and efficient analytical theory is presented to predict the breakdown voltage and electric field (E-field) distributions of Si/SiC LDMOS. The mechanism of surface electric field modulated and optimized by breakdown point transfer terminal technology is explained. Introducing the drain region impact factor into the analytical model to decouple the lateral and vertical depletion below the drift region. The analytical model proves that the deep drain region structure can modulate both the lateral and vertical electric field. Meanwhile, the location of the breakdown point can be determined by the E-field distribution at y = TDr and the E-field distribution at y = TSi, which is demonstrated by both theoretical interpreting and simulation. The derivations were verified using the ISE TCAD with a good agreement in the analytical model by changing the key structural parameters of the device. This analytical theory can be applied to other heterojunction power devices.

Impact of Left Side Back Gate Misalignment Effect in an Analytical Tunneling Current Modeling of an Ultrathin Asymmetric DG TFET

This paper exhibits a detailed explanation of an analytical band to band tunneling current model with gate misalignment effect for an ultrathin n type Asymmetric DG TFET considering fringing effect on the non gate overlapping channel region formed due to left side shifting of back gate. Model includes leakage current around the channel-drain interface, has a great impact in sub-threshold region and verified under front gate voltage with gate length scaled to 20 nm for different back gate shifts and various back gate voltages with Silicon Dioxide (SiO2) as gate insulator. It also exhibits a good concurrence with the device simulator in representing drain voltage dependent tunneling current characteristics with different front gate voltages. We authenticate our model throughout several simulations comparing device simulator ISE TCAD results and exhibits an excellent correlation.

Thermal Field Analysis for New AlGaN/GaN HEMT With Partial Etched AlGaN Layer

In order to explore the distribution of the device temperature field, this paper takes the new AlGaN/GaN HEMT with partial etched AlGaN layer as the research object. First, the ISE TCAD software is used to simulate the temperature field of AlGaN/GaN HEMT in two dimensions. The simulation results show a decrease of the maximum temperature and average junction temperature in the device channel with shorter thickness of the etched AlGaN layer. As the etching length increases, the hot spot temperature near the gate edge decreases, and the new hot spot position gradually shifts to the drain, which results in a more uniform distribution in the channel. Then, Raman spectroscopy is used to measure the channel junction temperature of AlGaN/GaN HEMTs. The results indicate that when the power dissipation is 0.3W and the etching depth is 5, 10, 15nm, the average channel junction temperature of the new etched AlGaN/GaN HEMT is 9.7%, 17.4% and 30.3% lower than that of the ordinary AlGaN/GaN HEMT, respectively. And the highest temperature of the new AlGaN/GaN HEMT also decreases. We can see that etching the barrier layer of AlGaN/GaN HEMT can not only improve the breakdown voltage, but also effectively reduce the channel junction temperature, and establish the relationship between the high power and thermal stability of the AlGaN/GaN HEMTs.

Simulation of SiC radiation detector degradation**Project supported by the National Key R&D Program of China (Grant No. 2016YFB0400400).

Simulation on the degradation of 4H-SiC Schottky detector was carried out using ISE TCAD, and the limit of the drift-diffusion analytical model was discussed. Two independent defect levels, rather than a pair of specific carrier lifetime, were induced to describe Z1/2 defects in simulation to calculate the charge collection efficiency versus bias voltage. Comparison between our calculation and the reported experimental results shows that an acceptable agreement was achieved, proving the feasibility of regarding Z1/2 defect as two individual defect levels. Such a treatment can simplify the simulation and may help to further investigate the detector degradation.

Analytical model of AlGaN/GaN HEMTs with a partial GaN cap layer

In this paper, a two-dimensional analytical model of AlGaN/GaN HEMTs with a partial GaN cap layer is developed. Under two assumptions of complete depletion and incomplete depletion, the analytical expressions for the channel potential and electric field distributions are obtained on the basis of Poisson's equation. The dependences of the channel potential and electric field distributions on various thicknesses and lengths of the partial GaN cap layer are demonstrated. The analytical model is verified in comparison with the ISE TCAD simulation. A fair consistency between the analytical and numerical results indicates the validity of the proposed analytical model. This method provides a reference to model other different GaN-based power devices.

Comparison of bulk FinFET and SOI FinFET

In this study, we compare the differences and advantages between Bulk FinFET and SOI FinFET. The results are simulated by using the ISE TCAD software. By changing the parameters of the gate voltage, drain voltage and gate length to analysis which characteristic is better. Through the experiment results, we demonstrate that the SOI FinFET have the better characteristics than bulk FinFET[1].

The effect of AlGaN bulk and AlGaN/GaN superlattice cladding layers on performance characteristics of deep violet InGaN DQW lasers

This paper reports performance characteristics of InGaN-based DQW laser diodes with different SLS cladding layer (CL) structures using the ISE TCAD software. LDs with SLSs as CLs were shown to have superior optical and electrical properties compared to LDs with bulk AlGaN CLs.The simulation results show the variation of output power, threshold current, slope efficiency, and differential quantum efficiency (DQE) from 13.51 to 10.88 mA, 20.92 to 41.27 mW, 1.83 to 1.87 W/A and 57.88 to 59.10%, for bulk to SLS CLs. Results show the increased operating current, electron and hole carrier densities and radiative recombination which enhanced output power and reduced threshold current for the structure with the SLS down CL. Using SLS in upper CL doesn't have significant effect on operating current, it increase the slope efficiency and DQE. Using SLS structure simultaneously in up and down CLs enhances the output power, DQE and slop efficiency, and decreases the threshold current.

Performance characteristics of deep violet InGaN DQW lasers based on different compliance layers

The performance characteristics of deep violet InGaN DQW LDs by varying material and thickness of compliance layer were numerically studied by ISE TCAD software. The In composition and thickness of compliance layer directly affect the operation current, which flow in the LD structure and its active region. The simulation results show that, lower In composition of the compliance layer causes higher operation current injection that results in higher electron and hole current densities in the active region, and output power. They also indicate that the LD differential quantum efficiency (DQE) and slope efficiency are increased, whereas output power and threshold current are decreased by increasing In composition of the compliance layer. The results also show that DQE and slope efficiency are increased, output power is decreased, whereas threshold current, on the average, is increased by increasing compliance layer thickness. Decreasing total output power with increasing compliance layer thickness can also be related to the operation current injected in LD structures, as well as electron and hole current densities which flow in LD structures and are injected in the active region. Lower compliance layer thickness causes higher operation current injection, resulting in higher electron and hole current densities and output power. Meanwhile lower stimulated emission rate in the active region with decreased compliance layer thickness results in lower slope efficiency and DQE.

Analytical model of LDMOS with a single step buried oxide layer

In this paper, a two-dimensional analytical model is established for the Single-Step Buried Oxide SOI structure proposed by the authors. Based on the two-dimensional Poisson equation, the analytic expression of the surface electric field and potential distributions for the device is achieved. In the SBOSOI (Single-Step Buried Oxide Silicon On Insulator) structure, the buried oxide layer thickness changes stepwise along the drift region, and the electric field in the oxide layer also varies with the different buried oxide layer thickness. These variations will modulate the surface electric field distribution through the electric field modulation effects, which makes the surface electric field distribution more uniform. As a result, the breakdown voltage of the device is improved by 60% compared with the conventional SOI structure.To verify the accuracy of the analytical model, the device simulation software ISE TCAD is utilized, the analytical values are in good agreement with the simulation results by the simulation software. The results verified the established two-dimensional analytical model for SBOSOI structure is valid, and it also illustrates the breakdown voltage enhancement by the electric field modulation effect sufficiently.The established analytical models will provide the physical and mathematical basis for further analysis of the new power devices with the patterned buried oxide layer.

Analytical model of LDMOS with a double step buried oxide layer

In this paper, a two-dimensional analytical model is established for the Buried Oxide Double Step Silicon On Insulator structure proposed by the authors. Based on the two-dimensional Poisson equation, the analytic expressions of the surface electric field and potential distributions for the device are achieved. In the BODS (Buried Oxide Double Step Silicon On Insulator) structure, the buried oxide layer thickness changes stepwise along the drift region, and the positive charge in the drift region can be accumulated at the corner of the step. These accumulated charge function as the space charge in the depleted drift region. At the same time, the electric field in the oxide layer also varies with the different drift region thickness. These variations especially the accumulated charge will modulate the surface electric field distribution through the electric field modulation effects, which makes the surface electric field distribution more uniform. As a result, the breakdown voltage of the device is improved by 30% compared with the conventional SOI structure.To verify the accuracy of the analytical model, the device simulation software ISE TCAD is utilized, the analytical values are in good agreement with the simulation results by the simulation software. That means the established two-dimensional analytical model for BODS structure is valid, and it also illustrates the breakdown voltage enhancement by the electric field modulation effect sufficiently.The established analytical models will provide the physical and mathematical basis for further analysis of the new power devices with the patterned buried oxide layer.

The influence of quaternary electron blocking layer on the performance characteristics of intracavity-contacted oxide-confined InGaN-based vertical cavity surface emitting lasers

The effect of electron blocking layer (EBL) on the performance characteristics of InGaN-based vertical cavity surface emitting lasers (VCSELs) was numerically investigated using an integrated system engineering technical computer aided design (ISE TCAD) simulation program. Simulation results indicated that the performance characteristics of InGaN quantum well VCSEL were improved by the ternary [Formula: see text] EBL. Better performance was also obtained when [Formula: see text] EBL was replaced by a polarization-matched [Formula: see text] EBL having the same energy bandgap. The quaternary EBL enhances the output power and differential quantum efficiency (DQE) as well as reduces the threshold current compared with the ternary EBL. Enhancement in the value of the optical intensity was also observed in the VCSEL structure with quaternary EBL. Furthermore, the effect of Al composition of AlInGaN EBL on the performance of InGaN-based VCSEL structure that uses the quaternary AlInGaN EBL was studied. In mole fraction was 0.115, Al mole fraction changed from 0.260 to 0.290 by step 0.005, and optimum performance was achieved in 0.275 Al mole fraction of AlInGaN EBL.

Effect of different EBL structures on deep violet InGaN laser diodes performance

Some specific designs on band structure near the active region, including the modifications of the material and thickness of the electron blocking layer (EBL), in the deep violet InGaN laser diodes (LDs) are investigated numerically with the ISE TCAD software. The analyses focus on electron and hole carrier injection efficiency, carrier distributions, electron leakage, and radiative recombination, subsequently, optical material gain, and optical intensity. The results indicate that for the ternary AlGaN EBL, the lowest threshold current and the highest output power, slope efficiency, and DQE have been obtained for the 15nm EBL thickness with 0.22 Al mole fraction. In addition, a comparative study has been conducted on the performance characteristics of the LD structures with a ternary AlGaN EBL and a quaternary AlInGaN EBL with an output emission wavelength at 390nm. The simulation results showed that the using quaternary AlInGaN EBL effectively improves the LD performance characteristics.

The effect of electron blocking layer on the performance of MQW oxide-confined intracavity-contacted InGaN-based vertical cavity surface emitting lasers

The effects of inserting AlGaN electron blocking layer (EBL) in the GaN-based vertical cavity surface emitting laser (VCSEL) structures on the LD performance has been investigated by Integrated System Engineering Technical Computer Aided Design (ISE TCAD) program software. The simulation results indicated that the performance characteristics of GaN-based quantum-well VCSEL were improved when the AlGaN EBL has been added. The effect of Al mole fraction (x) of the AlxGa1−xN EBL on the GaN-based VCSEL performance ranging from x=0.15 to x=0.25 was also studied. At x=0.15 to x=0.17, the threshold current was reduced. This reduction in the threshold current is due to the increase in the carrier confinement which is achieved by accumulated much more carrier close to the active region caused by the added AlxGa1−xN EBL. Above the x=0.17, the threshold current was increased which is attributed to the saturation of the carriers inside the active region that leads to increase in the leakage current. It also was due to that the EBL obstacle the hole flowing in the active region in the x>0.17. GaN-based VCSEL had the optimum performance with Al0.17Ga0.83N EBL; therefore, the effect of Al0.17Ga0.83N EBL thickness on the GaN-based quantum well VCSEL performance has also been investigated. According to the simulation results, the GaN-based VCSEL had the optimum performance when the EBL thickness was 25nm.

Physical mechanism of uniaxial strain in nano-scale metal oxide semiconductor transistor caused by sin film

Performance of a nano-scale MOS (metal-oxide-semiconductor) can be significantly improved by uniaxial stress, caused by the SiN film deposited on the surface of MOS. Although this technique has been widely used in the performance improvement of CMOS and integrated circuit, the physical mechanism for instance, how is the strain in MOS channel caused by the SiN film? how about the relation between the kinds of the structure of SiN film needed to be discussed in depth. On the basis of the ISE TCAD, three typical models for stress analysis——such as the segmentation structure model, the closed-loop structure model and the integrity structure model——are proposed. And then, this paper reveals the physical mechanism about how the stress in MOS channel is caused by the SiN film and how much the magnitude of the stress in MOS channel is induced. Results shows that: 1) The “step” structure is the necessary condition for the strain in the MOS channel to be caused by the SiN film. 2) With the tendency for SiN film to shrink or expand, the film may lead to the deformation along the MOS source/drain region of the Si material, which causes the deformation of Si in the channel. 3) The whole of the channel stress in SiN film is equal to the sum of the stress in the source/drain imposed by the SiN film above the source/drain, the stress which the “closed loop structure” applies to the channel, and the stress generated in the channel by the whole SiN film. Our conclusions may provide the valuable references to the manufacture of nano-scaled MOS and the research of the novel inducing stress technique.

Analysis and Simulation of Temperature and I-V Characteristics for SiC Schottky Barrier Diodes

In this paper, semiconductor simulation software ISE TCAD 10.0 was used to simulate W/SiC SBD forward voltage characteristics and reverse voltage characteristics at different temperatures on the basis of theoretical analysis, and the valuable results were achieved. Under the temperature range from 73 K to 773 K, the simulation results of W/SiC Schottky barrier diode forward voltage characteristics showed that forward characteristics were significant influenced by the temperature. At room temperature (303K), if bias voltage was low, the current will be exponential growing with voltage, and the turn-on voltage of W/SiC Schottky barrier diode was about 0.2V. If bias voltage was high, the current increased will be high, and the series resistance effect will become obvious. Under lower bias (2V), a different temperature from 73K to 573K had small impact on reverse current-voltage characteristics. The results showed that the device had the good rectifier characteristics, small reverse current, high breakdown voltage, and the device can steadily and long-term work in high temperature and other complex environment.

A two-dimensional analytical subthreshold behavior model for junctionless dual-material cylindrical surrounding-gate MOSFETs

A two-dimensional analytical subthreshold behavior model for junctionless dual-material cylindrical surrounding-gate (JLDMCSG) metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. It is derived by solving the two-dimensional Poisson's equation in two continuous cylindrical regions with any simplifying assumption. Using this analytical model, the subthreshold characteristics of JLDMCSG MOSFETs are investigated in terms of channel electrostatic potential, horizontal electric field, and subthreshold current. Compared to junctionless single-material cylindrical surrounding-gate MOSFETs, JLDMCSG MOSFETs can effectively suppress short-channel effects and simultaneously improve carrier transport efficiency. It is found that the subthreshold current of JLDMCSG MOSFETs can be significantly reduced by adopting both a thin oxide and thin silicon channel. The accuracy of the analytical model is verified by its good agreement with the three-dimensional numerical simulator ISE TCAD.

Modeling of parameters for nano‐scale surrounding‐gate MOSFET considering quantum mechanical effect

In this paper, an analytical surface potential and threshold voltage model for surrounding gate metal‐oxide semiconductor field‐effect transistor are proposed considering the quantum mechanical effect (QME). Considering variable Fermi potential along the channel, a simple relation between the eigen energies and the potential energy distribution is also provided for the first time. The variation of surface potential and the threshold voltage due to QMEs are computed analytically without using any numerical iteration technique in the model. QME on drain‐induced barrier lowering and threshold voltage roll‐off are also studied to provide a more accurate model. The proposed models are compared with existing surface potential and threshold voltage models and validated by comparing with the simulated results obtained from the 2D device simulator ATLAS of Integrated Systems Engineering Technology Computer Aided Design (ISE TCAD). Very good agreement of our model with TCAD is obtained for a wide variation of device parameters. Hence, the models will aid the designing of practical surrounding gate nano‐wire transistors. Copyright © 2013 John Wiley & Sons, Ltd.

Effects of traps and polarization charges on device performance of AlGaN/GaN high electron mobility transistors

This paper presents the simulated electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by using ISE TCAD software. The effects of interface traps, bulk traps and polarization charges are investigated. It was observed that the role and dynamic of traps affect the device performance which requires a precondition to calculate the DC characteristics that are in agreement with the experimental data. On the other hand, polarization charges lead to quantum confinement of the electrons in the channel and form two-dimensional electron gas. The electron quantization leads to increasing the drain current and shift in the threshold voltage. The device performance can be improved by optimizing the fixed interface charge and thus reducing the bulk traps to enhance the DC characteristics.