Analytical modelling and electrical characterisation of ZnO based HEMTs

Conventionally, Poisson’s equation coupled with 1-D Schrödinger’s equation is solved self-consistently in the triangular quantum well to calculate 2DEG density at the heterointerface. 2DEG density hence derived is a complicated transcendental function which cannot be solved analytically. Therefore, in this work, we use a simple expression for Fermi energy level to develop a compact physics-based 2D-analytical model for 2DEG density. The calculated 2DEG density from this model is validated with earlier reported experimental results. Using this 2DEG density, an expression for I-V characteristics of HEMTs has also been developed. The I-V characteristics of a buffer layer engineered MgZnO/CdZnO HEMT for improved 2DEG density have been analysed for the first time using developed model to the best of our knowledge.     

Compact analytical model for single gate AlInSb/InSb high electron mobility transistors

We have developed a 2D analytical model for the single gate Al In Sb/In Sb HEMT device by solving the Poisson equation using the parabolic approximation method.The developed model analyses the device performance by calculating the parameters such as surface potential,electric field distribution and drain current.The high mobility of the Al In Sb/In Sb quantum makes this HEMT ideal for high frequency,high power applications.The working of the single gate Al In Sb/In Sb HEMT device is studied by considering the variation of gate source voltage,drain source voltage,and channel length under the gate region and temperature.The carrier transport efficiency is improved by uniform electric field along the channel and the peak values near the source and drain regions.The results from the analytical model are compared with that of numerical simulations(TCAD) and a good agreement between them is achieved.     

基于表面势的GaN HEMT 集约内核模型

从器件表面势机理出发,考虑载流子浓度升高时费米势的变化,首次在二维泊松方程中引入新的费米势近似式,重构表面势源头方程,提出了一种直接基于表面势建立氮化镓高电子迁移率晶体管(GaN HEMT)器件模型的方法,建立了包括积累区和过渡区的物理基集约内核模型。表面势引入模型突破了现有的建模技术,给集约模型的建立提供可信的内核模型方程和理论基础。模型采用解析近似求解获得表面势,Pao-Sah模型验证可行性,I-V、C-V特性曲线与TCAD软件仿真的结果有很好的拟合,能准确描述各种偏置条件下GaN HEMT的电流、电荷特性。     

HEMT伏安特性

提出HEMT中二维电子气浓度的抛物线近似公式,建立了HEMT非线性电能荷控制模型.采用电子速场特性双折线近似计算了HEMT伏安特性,与实验数据符合良好.     

Multiband Mobility in Semiconducting Carbon Nanotubes

We present new data and a compact mobility model for semiconducting single-wall carbon nanotubes, with only two adjustable parameters, the elastic and inelastic collision mean free paths at 300 K. The mobility increases with diameter, decreases with temperature, and has a more complex dependence on charge density. The model and data suggest that the room temperature mobility does not exceed 10 000 cm²/Vmiddots at high carrier density (n > 0.5 nm^-1) for typical single-wall nanotube diameters, due to the strong scattering effect of the second subband.     

An analytical expression for Fermi level versus sheet carrierconcentration for HEMT modeling

A simple second-order analytical expression of Fermi-level variation with two-dimensional electron gas density in a high-electron-mobility transistor (HEMT) has been developed. This empirical expression was found to give better results near cutoff and in saturation than the linear approximation currently being used in many models. It can be used in the development of a more accurate charge control model and hence in the development of an improved analytical model for the HEMT     

Two-dimensional transient simulation of an idealized high electron mobility transistor

We develop a model for the high electron mobility transistor (HEMT) in which we include both hot-electron effects and conduction outside the quantum subband system using hydrodynamic-like transport equations. With such a model we can assess the significance of the various physical phenomena involved in the operation of the HEMT. We calculate results with a two-dimensional numerical technique for both steady-state and transient operation. For a 3-µm device at 77 K, we determine a transconductance of 450 mS/mm, a current-switching speed of 6 ps, and a capacitive charging speed of 4 ps/fanout gate which corresponds to the performance measured by other workers. We also see that electronic heating, velocity overshoot, and conduction outside the quantum well are significant near the pinchoff point. We conclude that the advantage of HEMT is twofold. The excellent conduction in the quantum well results in a low access resistance, and the low impurity concentration in the GaAs results in optimum overshoot effects.     

利用双势垒结构研究磁场下二维电子的态密度

势垒结构磁电容曲线，测量了垂直磁场下二维电子态密度。采用高斯型朗道态密度模型计算了双势垒结构的电容随磁场的变化曲线，与不同偏压和温度下的实验曲线符合得相当好，由此得到朗道能级模型态密度。根据拟合自洽地给出了二维浓度、费密能级、子带能量和有效Ｌａｎｄｅ因子随场振荡变化的规律。     

A surface-potential-based model for AlGaN/AlN/GaN HEMT

A new surface-potential-based model for AlGaN/AlN/GaN high electron mobility transistor(HEMT) is proposed in this paper. Since the high polarization effects caused by AlN interlayer favorably influence the two dimensional electron gas(2DEG) and scattering mechanisms, we first add spontaneous and piezoelectric charge terms to the source equation of surface-potential, and a mobility model for AlGaN/AlN/GaN HEMT is rewritten. Compared with TCAD simulations, the DC characteristics of AlGaN/AlN/GaN HEMT are faithfully reproduced by the new model.     

增强型GaN绝缘栅HEMT线性电荷控制解析模型

基于MIS理论和含极化的泊松方程,应用费米能级与二维电子气密度线性近似,并考虑计入了绝缘体/AlGaN界面的陷阱或离子电荷,导出建立了适用于增强型且兼容耗尽型AlGaN/GaN绝缘栅HEMT的线性电荷控制解析模型。研究表明,Insulator/AlGaN界面陷阱密度在1013cm-2数量级;基于该模型的器件转移特性的理论结果与器件的实测转移特性数据比较符合。该模型可望用于器件性能评估和设计优化。     

双异质结双平面掺杂HEMT器件的电荷控制模型

利用泊松方程以及异质结能带理论 ,通过费米能级 -二维电子气浓度的线性近似 ,推导了基于双异质结双平面掺杂的 HEMT器件的电荷控制模型 .计算分析了沟道顶部和底部平面掺杂浓度 ,栅金属与顶部平面掺杂层距离等材料结构尺寸和阈值电压、二维电子气浓度的关系 .该模型为优化和预测双平面掺杂 HEMT器件性能提供了一个有效手段     

Determination of energetic distribution of interface states betweengate metal and semiconductor in sub-micron devices from current-voltagecharacteristics

Density and energetic distributions of interface states between metal-semiconductor rectifying contacts in sub-micron GaAs MESFET and AlGaAs/InGaAs pseudomorphic high electron mobility transistors (HEMT's) have been studied. Electrical properties of the interface states between gate metal and semiconductor in sub-micron devices depend on growth technique, associated processing parameters and surface states on III-V semiconductors. Correlation between nonideal current-voltage (I-V) characteristics and interface states has been established through the bias dependence of ideality factor. Ideality factor determined from I-V characteristics of MESFET and HEMT increases with bias and then decreases after reaching a maximum. A theoretical model based on nonequilibrium approach has been used to determine the density of interface states and their energetic distribution from ideality factor. Essentially, Fermi level shifts with applied bias and Schottky barrier height changes due to trapping and detrapping of electrons by the interface states, and from these changes, density of interface states and their energetic distributions have been determined     

考虑量子效应的超薄体双栅肖特基源漏MOSFET电流解析模型

推导了超薄体双栅肖特基势垒MOSFET器件的漏电流模型,模型中考虑了势垒高度变化和载流子束缚效应.利用三角势垒近似求解薛定谔方程,得到的载流子密度和空间电荷密度一起用来得到量子束缚效应.由于量子束缚效应的存在,第一个子带高于导带底,这等效于禁带变宽.因此源漏端的势垒高度提高,载流子密度降低,漏电流降低.以前的模型仅考虑由于镜像力导致的肖特基势垒降低,因而不能准确表示漏电流.包含量子束缚效应的漏电流模型克服了这些缺陷.结果表明,较小的非负肖特基势垒,甚至零势垒高度,也存在隧穿电流.二维器件模拟器Silvaco得到的结果和模型结果吻合得很好.     

非量子限条件下P型InSbMOS结构反型层中子能带实验研究

在100K条件下测量了p型InSb MOS器件的变频电容-电压(C-V)谱,在反型区观察到第二子带填充电子的台阶效应,还发现一个位于导带中的共振缺陷态.采用非量子限多带C-V拟合模型获得了子能带结构.     

Electrical properties and limiting position of the fermi level in InSb irradiated with protons

The results of experimental and simulation studies of electrical parameters and the limiting position of the Fermi level in metallurgically and transmutationally doped InSb irradiated with protons (10 MeV, 2×10¹⁶ cm^?2, 300 K) are reported. It is shown that the limiting electrical parameters of irradiated InSb correspond to a p-type material. Special features of the annealing of radiation defects are studied in the temperature range 20–500°C.     

Self-consistent analysis of the band structure of doped lattice-matched GaNAsBi-based QWs operating at 1.55 μm

Band structures of n–i doped lattice-matched GaNAsBi/GaAs quantum wells are studied theoretically using a self-consistent calculation (based on the envelop function formalism) combined with the 16-band anti-crossing model. Operating at 1.55 μm, these QWs can represent active zones of temperature-insensitive optoelectronic device applications intended for optical fiber communications. We have calculated physical parameters of the structures such as the confining potential profiles, the Fermi level, the subband energies and their corresponding wavefunctions as well as the oscillator strength of inter-band transitions, the subband occupations, and the confined electrons density distributions. Finally, the absorption coefficient spectra of GaNAsBi-based QWs are also computed.     

一种紧凑的GaN高电子迁移率晶体管大信号模型拓扑

GaN高电子迁移率晶体管（HEMT）以其复杂的器件特性使其大信号建模变得十分困难,尽管EEHEMT、Angelov等模型结构曾经成功应用于GaAs HEMT/MESFET的大信号模型,但当它们被用于GaN HEMT建模时却不再准确和完备.面向GaN HEMT器件的大信号模型,本文提出了一种紧凑的模型拓扑,此模型拓扑综合了GaN HEMT器件的直流电压-电流（I-V）特性、非线性电容、寄生参数、栅延迟漏延迟与电流崩塌、自热效应以及噪声等特性.经验证此模型拓扑在仿真中具有很好的收敛性,适用于GaN HEMT器件的大信号模型的建立,满足GaN基微波电路设计对器件模型的需求.     

A 2DEG charge density based drain current model for various Al and In molefraction mobility dependent nano-scale AlInGaN/AlN/GaN HEMT devices

We present a two-dimensional electron gas（2DEG） charge-control mobility variation based drain current model for sheet carrier density in the channel.The model was developed for the AlInGaN/AlN/GaN highelectron -mobility transistor.The sheet carrier density model used here accounts for the independence between the Fermi levels E_f and n_s along with mobility for various Al and In molefractions.This physics based ns model fully depends upon the variation of E_f,u0,the first subband E₀,the second subband E\,and n_s.We present a physics based analytical drain current model using n_s with the minimum set of parameters.The analytical results obtained are compared with the experimental results for four samples with various molefraction and barrier thickness.A good agreement between the results is obtained,thus validating the model.     

An improved large signal model of InP HEMTs

An improved large signal model for InP HEMTs is proposed in this paper.The channel current and charge model equations are constructed based on the Angelov model equations.Both the equations for channel current and gate charge models were all continuous and high order drivable,and the proposed gate charge model satisfied the charge conservation.For the strong leakage induced barrier reduction effect of InP HEMTs,the Angelov current model equations are improved.The channel current model could fit DC performance of devices.A 2 × 25μm × 70 nm InP HEMT device is used to demonstrate the extraction and validation of the model,in which the model has predicted the DC I-V,C-Vand bias related S parameters accurately.     

30 nm T-gate enhancement-mode InAlN/AlN/GaN HEMT on SiC substratesfor future high power RF applications

The DC and RF performance of 30 nm gate length enhancement mode (E-mode) InAlN/AlN/GaN high electron mobility transistor (HEMT) on SiC substrate with heavily doped source and drain region have been investigated using the Synopsys TCAD tool. The proposed device has the features of a recessed T-gate structure, InGaN back barrier and Al₂O₃ passivated device surface. The proposed HEMT exhibits a maximum drain current density of 2.1 A/mm, transconductance g_m of 1050 mS/mm, current gain cut-off frequency f_t of 350 GHz and power gain cut-off frequency f_max of 340 GHz. At room temperature the measured carrier mobility (μ), sheet charge carrier density (n_s) and breakdown voltage are 1580 cm²/(V·s), 1.9×10¹³ cm^-2, and 10.7 V respectively. The superlatives of the proposed HEMTs are bewitching competitor or future sub-millimeter wave high power RF VLSI circuit applications.