ISE TCAD Research Articles

Study on effect of quantum well number on performance characteristics of GaN-based vertical cavity surface emitting laser

The effect of number of quantum wells and quantum well thickness on the optical performance of InGaN vertical cavity surface emitting laser (VCSEL) was numerically investigated using Integrated System Engineering Technical Computer Aided Design (ISE TCAD) simulation program. The simulation results indicated that the output power and differential quantum efficiency of the double quantum well (DQW) laser were increased and threshold current decreased as compared to the single and triplet quantum wells VCSEL. Threshold current enhancement in the single quantum well (SQW) is attributed to the electron carrier leakage increasing from active layers because of the lower optical confinement factor. Simulation results show that in the double quantum well, the optical material gain and electron and hole carrier densities are approximately uniform with respect to the SQW and TQW. Also these results indicated that the electron current density in the DQW is the lowest. In the active region, electrical field decreased for the double quantum well because of the built-in electrical field reduction inside the quantum well. Finally the effect of quantum well thickness in DQW GaN-based VCSEL was investigated and it was observed that DQW VCSEL with 3nm quantum wells thickness had the optimum threshold current.

Simulation analysis of electrical characteristics of strained SiGe channel-on-insulator p-MOSFET

利用数值模拟软件ISE TCAD对绝缘层上应变SiGe(SGOI)和Si(SOI)p-MOSFET的电学特性进行了二维数值模拟.计算结果表明，与传统的SOI p-MOSFET相比，SGOI p-MOSFET的漏源饱和电流几乎要高出两倍; 其亚阈值电流要高出1～3个数量级.Ge合金组分作为应变SiGe沟道MOSFET的重要参数，就不同Ge合金组分对SGOI p-MOSFET的电学特性的影响也进行了较为深入的研究.随着Ge合金组分的增大，SGOI p-MOSFET的总体电学性能有所提高.;In this paper, the strained SiGe-on-Insulator (SGOI) p-MOSFET and Si-on-Insulator (SOI) p-MOSFET are respectively studied via 2-D numerical simulation by ISE TCAD software. The results indicate that compared with the conventional SOI p-MOSFET, the drain-source saturation current of SGOI p-MOSFET almost more than twice, the sub-threshold current of SGOI p-MOSFET has 1～3 orders of magnitude higher than that of SOI p-MOSFET. Because Ge alloy mole fraction is an important basic parameter to the strained SiGe channel MOSFET, the effect of Ge alloy mole fraction on the electrical characteristics of the SGOI p-MOSFET is in depth study in this paper. With the increasing of Ge alloy mole fraction, the overall electrical properties of SGOI p-MOSFET are improved.The strained SiGe-on-Insulator (SGOI) p-MOSFET and Si-on-Insulator (SOI) p-MOSFET were studied via 2-D numerical simulation by ISE TCAD software, respectively. The results indicate that the drain-source saturation current of SGOI p-MOSFET is almost more than twice that of conventional SOI p-MOSFET. The sub-threshold current of SGOI p-MOSFET is 1～3 orders of magnitude higher than that of SOI p-MOSFET. Because Ge alloy mole fraction is an important parameter for the strained SiGe channel MOSFET, its effect on the electrical characteristics of the SGOI p-MOSFET was studied in detail. With the increasing of Ge alloy mole fraction, the overall electrical properties of SGOI p-MOSFET were improved.

Effects of Cavity Length on Optical Characteristics of Deep Violet InGaN DQW Lasers

The performance characteristics and their dependence to cavity length of deep violet InGaN DQW lasers emitting at 390 nm have been investigated using the Integrated System Engineering Technical Computer Aided Design (ISE TCAD) software. The focus of simulation was on the study of optical properties which were carried out with varying cavity length from 200µm to 600µm. The simulation results indicated that the cavity length strongly affects the optical properties of the violet InGaN DQW laser. They showed that the parameters related to the output power such as optical intensity increases by increasing cavity length due to increase of applied current to the laser system. The results also indicated that the parameters such as optical material gain, stimulated and radiative recombination which are related to quantum efficiencies and laser performance decrease by increasing cavity length. It was shown that the laser structure with the longer cavity length has the lower optical loss.

Performance enhancement of deep violet indium gallium nitride double quantum well lasers using delta barrier close to electron blocking layer

A thin aluminum gallium nitride (AlGaN) electron blocking layer (EBL), above the active region, is used to improve the performance and reduce threshold current of indium gallium nitride (InGaN) quantum well (QW) lasers. A new structure, with delta barrier close to EBL (AlGaN/0.3 nm GaN/InGaN), was devised to prevent deleterious polarization effects and confer other advantages. The effect of a 0.3 nm-thick GaN delta barrier on the performance of a deep violet InGaN double QW laser was investigated using ISE TCAD software. The results indicate that the delta barrier significantly enhances the output power, slope efficiency and external differential quantum efficiency while decreasing the threshold current.

Holding-voltage drift of a silicon-controlled rectifier with different film thicknesses in silicon-on-insulator technology

This paper presents a new phenomenon, where the holding-voltage of a silicon-controlled rectifier acts as an electrostatic-discharge protection drift in diverse film thicknesses in silicon-on-insulator (SOI) technology. The phenomenon was demonstrated through fabricated chips in 0.18 μm SOI technology. The drift of the holding voltage was then simulated, and its mechanism is discussed comprehensively through ISE TCAD simulations.

Study of modeling for hetero-materiel gate fully depleted SSDOI MOSFET

In this paper,we propose a new device structure called HMG SSDOI (hetero-materiel gate strained Si directly on insulator), which combines the advantages of strained-silicon and hetero-material gate technology. By solving 2D Poisson's equation, we present models of the surface potential, surface electric field and threshold voltage for the new structure. These models take into account the effects of the gate length, the work function and the energy band. ISE TCAD is also used to simulate the performance of new device structure. The comparison results of model calculation and mathematic simulation show that the new structure of HMG SSDOI can enhance the carrier transport efficiency and suppress short channel effect, drain induction barrier lower and hot carrier effect, which improves device performance greatly.

Generalized Early Voltage Model of Bipolar Transistors for Linearly Graded Germanium in Base

The standard Early voltage of the SPICE Gummel-Poon model (SGP) is generalized for SiGe npn heterojunction bipolar transistors (HBTs). An accurate model for Early effects compatible with the SGP model is obtained considering graded germanium induced bandgap narrowing effect in the base in modern SiGe HBTs and simplified to a compact model which is consistent with ISE TCAD simulation results. The presentation of the Early effect model is significant for the design and simulation of the high performance SiGe BiCMOS technology.

The effects of quantum wells number and the built-in polarization on the performance of quaternary AlInGaN UV laser diode

The performance of quaternary Al0.08In0.08Ga0.84N multi-quantum well (MQW) laser diodes (LDs) using the simulation program of Integrated System Engineering Technical Computer Aided design (ISE TCAD) was studied. The simulation results show that the low threshold current, high output power and slope efficiency can be obtained when the quantum wells number is 4. Although, the fourth quantum well which placed in the right side (n-side) of the active region has a negative value of optical gain this means that the optical gain does not occur in this quantum well of laser structure. However, high external differential quantum efficiency (DQE) inside the active region was also observed. Optical gain and intensity were increased when the numbers of quantum wells increase reached 4. The built-in electric field effect inside the quantum well leads to the reduction of the overlap integral between the electrons and holes by separating their wave function was included. As well as, Al0.25In0.08Ga0.67N electron blocking layer (EBL) employed to enhance the performance of Al0.08In0.08Ga0.84N MQW LDs by increasing the optical confinement factor (OCF) inside the quantum wells.

An analytical model for the surface electrical field distribution of LDMOSFETs with shield rings

An analytical model of an LDMOSFET with a shield ring is established according to the 2D Poisson equation. Surface electrical field distribution along the drift region is obtained from this model and the influence of shield length and oxide thickness on the electrical field distribution is studied. The robustness of this model is verified using ISE TCAD simulation tools. The breakdown voltage of a specific device is also calculated and the result is in good agreement with experimental data.

Early effect modeling of silicon-on-insulator SiGe heterojunction bipolar transistors

Silicon germanium (SiGe) heterojunction bipolar transistor (HBT) on thin silicon-on-insulator (SOI) has recently been demonstrated and integrated into the latest SOI BiCMOS technology. The Early effect of the SOI SiGe HBT is analysed considering vertical and horizontal collector depletion, which is different from that of a bulk counterpart. A new compact formula of the Early voltage is presented and validated by an ISE TCAD simulation. The Early voltage shows a kink with the increase of the reverse base—collector bias. Large differences are observed between SOI devices and their bulk counterparts. The presented Early effect model can be employed for a fast evaluation of the Early voltage and is useful to the design, the simulation and the fabrication of high performance SOI SiGe devices and circuits.

Quaternary ultraviolet AlInGaN MQW laser diode performance using quaternary AlInGaN electron blocking layer

The effect of polarization-matched Al(0.25)In(0.08)Ga(0.67)N electron-blocking layer (EBL) on the optical performance of ultraviolet Al(0.08)In(0.08)Ga(0.84)N/Al(0.1)In(0.01)Ga(0.84)N multi-quantum well (MQW) laser diodes (LDs) was investigated. The polarization-matched Al(0.25)In(0.08)Ga(0.67)N electron blocking layer (EBL) was employed in an attempt to reduce the polarization effect inside the active region of the diodes. The device performance which is affected by piezoelectric was studied via drift-diffusion model for carrier transport, optical gain and losses using the simulation program of Integrated System Engineering Technical Computer Aided design (ISE TCAD). The optical performance of the LD using quaternary Al(0.25)In(0.08)Ga(0.67)N EBL was compared with the LD using ternary Al(0.3)Ga(0.7)N EBL where both materials have the same energy band gap of Eg = 3.53 eV. The self-consistent ISE-TCAD simulation program results showed that the polarization-matched quaternary Al(0.25)In(0.08)Ga(0.67)N EBL is beneficial as it confines the electrons inside the quantum well region better than ternary Al(0.3)Ga(0.7)N EBL. The results indicated that the use of Al(0.25)In(0.08)Ga(0.67)N EBL has lower threshold current and higher optical intensity than those for Al(0.3)Ga(0.7)N EBL. The effect of Al(0.25)In(0.08)Ga(0.67)N EBL thickness on the performance of LDs has also been studied. Results at room temperature indicated that lower threshold current, high slope efficiency, high output power, and high differential quantum efficiency DQE occurred when the thickness of Al(0.25)In(0.08)Ga(0.67)N EBL was 0.25 µm.

Avalanche behavior of power MOSFETs under different temperature conditions

The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation. The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range (−55 to 150 °C). An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism. The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature. The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.

An improved analytical model for the electric field distribution in an RF-LDMOST structure

This paper presents an improved analytical model for an RF-LDMOST structure based on the 2D Poisson equation. The derived model indicates the influence of high doped shallow drift and low doping concentration p epitaxial layer on the electric field distribution. In particular, the importance of the thickness of the p epitaxial layer for electric field distributions in RF-LDMOST are shown through MATLAB analytical results based on the model. Then ISE TCAD simulations and experiments are processed and their results are in agreement with the analytical model. This model contributes to the comprehension and optimization design of RF-LDMOST.

ELECTRICAL PROPERTIES OF AlGaN/GaN HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS (HFETs) WITH AND WITHOUT Mg-DOPED CARRIER CONFINEMENT LAYER

AlGaN/GaN -based heterostructure field-effect transistors (HFETs) with and without Mg -doped semi-insulating carrier confinement layer were simulated by using ISE TCAD software, respectively. The detailed study on the electrical properties of these samples was performed. The effect of inserting Mg -doped GaN layer on the source–drain (S–D) leakage current was investigated. Higher values of drain current and extrinsic transconductance were achieved with conventional HFETs (without Mg -doped). The source-to-drain (S–D) leakage current of conventional HFETs was also higher. However, the S–D leakage current was reduced with the insertion of the Mg -doped semi-insulating carrier confinement layer. Our results are in good agreement with the experimental results obtained by other researchers.

A comparative study of self-heating effect of nMOSFETs fabricated on SGOI and SGSOAN substrates

In this work, for the first time, the electrical and thermal characteristics of strained Si/SiGe nanoscale n type metal–oxide–silicon field-effect transistors (MOSFETs) with silicon-on-aluminum nitride (SOAN) substrate are investigated by ISE TCAD. This novel structure is named as SGSOAN nMOSFET. A comparative study of self-heating effect (SHE) of nMOSFETs fabricated on SGOI and SGSOAN are presented in this paper. Numerical study results show that this novel SGSOAN structure can greatly eliminate excessive self-heating in devices, which gives a more promising application for SGOI to work at high temperature.

Simulation research on offset field-plate used as edge termination in 4H–SiC merged PiN-Schottky diodes

A new structure of 4H–silicon carbide (SiC) merged PiN-Schottky (MPS) diodes with offset field-plate (FP) as edge termination is developed. To understand the influences of 4H–SiC MPS diodes with offset FP on the characteristics, simulations have been done by using ISE TCAD. Related factors of offset FP have been studied as well to optimise the reverse characteristics of 4H–SiC MPS diodes. The simulation results show that the device using offset FP can create a higher blocking voltage under reverse bias as compared with that using field guard rings. Besides, the offset FP does not cause any extra steps in the manufacture of MPS diodes.

InGaN MQW violet laser diode performance with quaternary AlInGaN blocking layer

Violet laser diode performance with AlInGaN blocking layer has numerically been investigated by using ISE TCAD software simulation program. The effects of AlInGaN blocking layer have been studied from different perspectives, the threshold current, output power, optical intensity, and temperature characteristics. In this study, simulation results indicated that the use of AlGaInN instead of the conventional AlGaN blocking layer leads to decreasing the threshold current while this blocking layer increases the optical intensity and output power when the mole fractions of Al and Ga are carefully chosen. The laser diode survives above 370 K.

High breakdown voltage AlGaN/GaN HEMTs employing fluoride plasma treatment

We proposed channel-modulated AlGaN/GaN high electron mobility transistors (HEMTs) employing fluoride plasma treatment and carried out a detailed numerical simulation of device operation using ISE TCAD software. A reduction of peak electric field is required for achieving the high breakdown voltage of AlGaN/GaN HEMTs. The proposed channel-modulated AlGaN/GaN HEMTs created the fluoride plasma-treated region between the gate and the drain. The fluoride plasma-treated region modulated the two-dimensional electron gas (2-DEG) channel concentration, and effectively reduced the peak electric field without any field plates. The reduction of peak electric field in the gate-to-drain region caused the breakdown voltage to increase by 206%. The dc characteristics of channel-modulated AlGaN/GaN HEMTs remained practically the same as those of the conventional AlGaN/GaN HEMTs. The breakdown voltage could be increased without a significant degradation of dc characteristics due to the SiO2 passivation layer. The deposition of the SiO2 passivation layer combined with fluoride plasma treatment is a powerful process for channel-modulated AlGaN/GaN HEMTs.

On the reverse short‐channel effect and threshold voltage roll‐off controls for 90 nm node MOSFETs

In order to let device designers tune the short channel behavior of MOSFETs, a method is proposed in this work to demonstrate how to use LDD (lightly doped drain) and pocket implants to control RSCE (reverse short channel effect) and threshold voltage (Vt ) roll‐off. The method is based on the process parameters and silicon data of the 90 nm node technology of UMC (United Microelectronics Corporation). With the help of computers, 17 different process conditions of 8 different gate lengths were simulated using ISE TCAD to collect Vt variation data. Four characteristics representing the short channel behaviors of the MOSFETs were designed and extracted from the simulated data. Their empirical equations were also established subsequently. After verification, those mathematical models were demonstrated to help device designers in choosing the most suitable LDD and pocket implant parameters to generate required Vt characteristics.

A threshold voltage model for short-channel MOSFETs taking into account the varying depth of channel depletion layers around the source and drain

In this paper, an analytical model for threshold voltage of short-channel MOSFETs is presented. For such devices, the depletion regions due to source/drain junctions occupy a large portion of the channel, and hence are very important for accurate modeling. The proposed threshold voltage model is based on a realistic physically-based model for the depletion layer depth along the channel that takes into account its variation due to the source and drain junctions. With this, the unrealistic assumption of a constant depletion layer depth has been removed, resulting in an accurate prediction of the threshold voltage. The proposed model can predict the drain induced barrier lowering (DIBL) effect and hence, the threshold voltage roll-off characteristics quite accurately. The model predictions are verified against the 2-D numerical device simulator, DESSIS of ISE TCAD.