Monolithic Integration of InGaP/AlGaAs/InGaAs Enhancement/Depletion-Mode PHEMTs

提出了一种新结构单片集成增强/耗尽型(E/D)InGaP/AlGaAs/InGaAs赝配高电子迁移率晶体管(PHEMTs).外延层材料通过分子束外延技术生长,在室温下,其电子迁移率和二维电子气浓度分别为5410cm2/(V·s)和1.34×1012cm-2.首次提出了普通光学接触曝光分步制作增强与耗尽型的栅技术方法.研制出了单片集成E/D型PHEMTs,获得良好的直流和交流特性,最大饱和漏电流密度分别为300和340mA/mm,跨导为350和300mS/mm,阈值电压为0.2和-0.4V,增强型的fT和fmax为10.3和12.4GHz,耗尽型的fT和fmax为12.8和14.7GHz.增强/耗尽型PHEMTs的栅漏反向击穿电压都为-14V.     

GaAs基单片集成InGaP／AIGaAs／InGaAs增强／耗尽型PHEMTs

提出了一种新结构单片集成增强/耗尽型(E/D)InGaP/AlGaAs/InGaAs赝配高电子迁移率晶体管(PHEMTs).外延层材料通过分子束外延技术生长,在室温下,其电子迁移率和二维电子气浓度分别为5410cm2/(V·s)和1.34×1012cm-2.首次提出了普通光学接触曝光分步制作增强与耗尽型的栅技术方法.研制出了单片集成E/D型PHEMTs,获得良好的直流和交流特性,最大饱和漏电流密度分别为300和340mA/mm,跨导为350和300mS/mm,阈值电压为0.2和-0.4V,增强型的fT和fmax为10.3和12.4GHz,耗尽型的fT和fmax为12.8和14.7GHz.增强/耗尽型PHEMTs的栅漏反向击穿电压都为-14V.     

GaAs基单片集成InGaP/AlGaAs/InGaAs增强/耗尽型PHEMTs

提出了一种新结构单片集成增强/耗尽型(E/D)InGaP/AlGaAs/InGaAs赝配高电子迁移率晶体管(PHEMTs).外延层材料通过分子束外延技术生长,在室温下,其电子迁移率和二维电子气浓度分别为5410cm2/(V·s)和1.34×1012cm-2.首次提出了普通光学接触曝光分步制作增强与耗尽型的栅技术方法.研制出了单片集成E/D型PHEMTs,获得良好的直流和交流特性,最大饱和漏电流密度分别为300和340mA/mm,跨导为350和300mS/mm,阈值电压为0.2和-0.4V,增强型的fT和fmax为10.3和12.4GHz,耗尽型的fT和fmax为12.8和14.7GHz.增强/耗尽型PHEMTs的栅漏反向击穿电压都为-14V.     

采用耗尽型作负载的高性能N型沟道MOS大规模集成电路

采用耗尽型MOS场效应晶体管(MOSFET)作为负载元件的含意已有认识,且提出了某些器件结构。然而在一个片子上同时制作增强型及耗尽型两种MOSFET是难行的。本文描述采用N型沟道增强型及耗尽型MOSFET的新颖的高速集成电路。集成电路的剖面图示于图1。增强型MOSFET具有一覆盖在热生长二氧化硅的三氧化二铝层来作为栅绝缘物。其阈值电压可由改变二氧化硅与三氧化二铝层的厚度比(SiO_2/Al_2O_3)来控制,直到+1伏、+5伏电源电压均能工作时,这些增强型MOSFET的电     

E/D型HEMT DCFL倒相器

<正> 一、引言为了满足超高速计算机、高速数据处理和卫星通信等高性能电子系统的迫切需要,人们一直在寻求和开发新的超高速和微波器件。利用异质界面二维电子气(2DEG)高迁移率特性的高电子迁移率晶体管(HEMT)及其IC已显示出巨大的发展潜力和广阔的应用前景。因而成为最有希望的候选者之一。以增强型(E型)HEMT为开关管、耗尽型(D型)HEMT(或饱和电阻)为负载的E/D(或E/R)型直接耦合场效应晶体管逻辑     

调制掺杂(Al,Ga)As-GaAs异质结二维电子气场效应晶体管(TEGFET)

调制掺杂(Al,Ga)As-GaAs异质结二维电子气场效应晶体管(TEGFET)是一种基于(Al,Ga)As-GaAs的界面处存在着高载流子迁移率二线电子气的原理制成的一种新型场效应器件.科学家们预言这种器件将在微波领域及超高速超大规模集成电路中得到重要应用.本文简述了它的工作机理、基本结构、耗尽型及增强型模式、工艺制造、目前达到的性能与通常的GaAs FET的比较、初步的器件物理分析和伏安特性计算.着重指出分子束外延生长工艺是这种器件的关键工艺.     

一种P-GaN栅结合混合帽层结构的HEMT器件

为了进一步提升P-GaN栅HEMT器件的阈值电压和击穿电压,提出了一种具有P-GaN栅结合混合掺杂帽层结构的氮化镓高电子迁移率晶体管(HEMT)。新器件利用混合掺杂帽层结构,调节整体极化效应,可以进一步耗尽混合帽层下方沟道区域的二维电子气,提升阈值电压。在反向阻断状态下,混合帽层可以调节栅极右侧电场分布,改善栅边电场集中现象,提高器件的击穿电压。利用Sentaurus TCAD进行仿真,对比普通P-GaN栅增强型器件,结果显示,新型结构器件击穿电压由593 V提升至733 V,增幅达24%,阈值电压由0.509 V提升至1.323 V。     

增强型GaN HEMT器件的实现方法与研究进展

考虑到实际应用对可靠性、设计成本及能耗的要求,增强型GaN高电子迁移率晶体管（HEMT）器件比传统耗尽型GaN HEMT器件优势更显著。目前有许多方法可以实现增强型GaN HEMT器件,如使用p型栅技术、凹栅结构、共源共栅（Cascode）结构、氟离子处理法、薄势垒AlGaN层以及它们的改进结构等。分别对使用以上方法制备的增强型GaN HEMT器件进行了综述,并对增强型GaN HEMT器件的最新研究进展进行了总结,探索未来增强型GaN HEMT器件的发展方向。     

单片集成0.8μm栅长GaAs基InGaP/AlGaAs/InGaAs增强/耗尽型赝配高电子迁移率晶体管

优化了GaAs基InGaP/AlGaAs/InGaAs赝配高电子迁移率晶体管(PHEMT)的外延结构,有利于获得增强型PHEMT的正向阈值电压.采用光学接触式光刻方式,实现了单片集成0.8μm栅长GaAs基InGaP/AlGaAs/InGaAs增强/耗尽型PHEMT.直流和高频测试结果显示:增强型(耗尽型)PHEMT的阈值电压、非本征跨导、最大饱和漏电流密度、电流增益截止频率、最高振荡频率分别为0.1V(-0.5V),330mS/mm(260mS/mm),245mA/mm(255mA/mm),14.9GHz(14.5GHz)和18GHz(20GHz).利用单片集成增强/耗尽型PHEMT实现了直接耦合场效应晶体管逻辑反相器,电源电压为1V,输入0.15V电压时,输出电压为0.98V;输入0.3V电压时,输出电压为0.18V.     

沟道大电流感应n沟金属-氧化物-半导体场效应晶体管栅氧化层的加速击穿

本文研究n沟金属-氧化物-半导体场效应晶体管(MOSFET’s)的栅氧化层的击穿特性。由于受导电沟道横向电场产生的沟道大电流的影响,MOSFET’s的栅氧化层的动态击穿场强远低于有相同栅氧化层的MOS电容器的静态击穿场强。耗尽型MOSFET’s的栅氧化层动态击穿场强主要由漏-源穿通电压决定,而增强型器件主要由深耗尽层击穿电压决定。无论是耗尽型还是增强型器件,栅电压在一定范围内增加时,栅氧化层动态击穿场强下降。     

A model for the current—Voltage characteristics of MODFET's

A model for theI-Vcharacteristics of MODFET's is presented. In this paper, an analytic velocity-field model is used. To more accurately describe the physical characteristics of MODFET's, the model of this paper is divided into two regions (the linear region and the saturation region), being continuous at the pinchoff voltage, and includes the diffusion component in addition to the drift component of current. Using this model, the simulatedI-Vcharacteristics are in excellent agreement with the experimental data.     

GaInP/InGaAs/GaAs graded barrier MODFET grown by OMVPE: design,fabrication, and device results

Ga_xIn_1-xP/Ga_yIn_1-x As/GaAs Modulation Doped Field Effect Transistors (MODFET's) with a pseudomorphic barrier and a pseudomorphic channel were grown by Organo Metallic Vapor Phase Epitaxy (OMVPE). This material system is promising for advanced MODFET's on GaAs for high frequency and power applications, because of the large discontinuity in the conduction band, advantages in the processing and the capability to increase the energy separation between the bottom of the conduction band and Fermi level by compositionally grading the barriers. Record 2-dimensional Electron Gas (2-DEG) carrier densities of 3.1·10¹² cm^-2 for single-sided MODFET's were measured. Measured RF power at 10 GHz for 0.25 pm devices was ⩾0.4 W/mm. For the first time cutoff frequencies f_T and f_max exceeding 105 and 188 GHz, respectively, were obtained for this material system with 0.1 μm gate-length MODFET's     

Parasitic MESFET in (Al, Ga) As/GaAs modulation doped FET's and MODFET characterization

A charge-control model for n-channel modulation doped FET's (MODFET's) is extended to include the drain-to-source current through the doped (Al, Ga)As layer which becomes important for large positive gate voltages. This parasitic conduction leads to decreased device transconductances at high gate voltages. A unified and complete characterization technique for deducing the parameters of our model is introduced and used for the device characterization. Parameters, e.g., the saturation velocity, two-dimensional gas concentration at equilibrium, thickness of the doped (Al, Ga)As layer, etc., deduced using the model, are in good agreement with the independent calculations and measurements. However, the deduced values of the room-temperature low field mobility of the two-dimensional electron gas are considerably smaller than those measured by Hall effect and in long-gate MODFET's. This model is in good agreement with the characteristics of high-current normally on MODFET's. The maximum measured current swing of 300 mA/mm gate is reported.     

Inverted GaAs/AlGaAs modulation-doped field-effect transistors with extremely high transconductances

Inverted GaAs/AsGaAs MODFET's with transconductances as high as 1810 mS/mm at 77 K and 1180 mS/mm at 300 K are fabricated using a self-aligned process. The devices have the gate-heterojunction interface spacing of only 100 Å, and the observed values of the transconductance are limited primarily by the source series resistance and by the gate current. The MODFET characteristics are interpreted using the charge control velocity saturation model which takes into account the gate current. The obtained results show a great potential of inverted MODFET's for ultrahigh-speed applications.     

Nonlinear charge control in AlGaAs/GaAs modulation-doped FET's

A new model for nonlinear charge control in normally on modulation-doped field-effect transistors (MODFET's) is proposed. It is shown that conventional charge control models are insufficient to describe MODFET's with large negative pinchoff voltages, and that the depletion approximation is inaccurate in circumstances where the layer dimensions become of the order of a Debye length. The new model is based upon a one-dimensional numerical solution of Poisson's equation and the drift-diffusion equation. It also takes into account the shift in the 2DEG position with gate bias, and parallel conduction in the doped AlGaAs layer. The effect of nonlinear charge control on MODFET transconductance is considered by combining the new model with a two-dimensional analytic representation of the MODFET.     

Backgating characteristics of MODFET structures

Significant backgating in mesa-isolated AlGaAs/GaAs MODFET structures is reported. Results are presented on the influence of backgate potential on the electrical characteristics of enhancement-mode MODFET's fabricated on MBE grown material. An observed zero threshold voltage for the onset of backgating is attributed to a high level of current leakage in the high-purity GaAs buffer layer. Transconductance and capacitance-voltage measurements on MODFET's show that the backgate potential influences primarily the electrical properties of the 2-D electron gas channel and the adjacent AlGaAs layer.     

GaAs/AlGaAs and InGaAs/AlGaAs MODFET inverter simulations

Although MODFET's have exhibited the fastest switching speed for any digital circuit technology, there is as yet no clear consensus on optimal inverter design rules. We therefore have developed a comprehensive MODFET device model that accurately accounts for such high gate bias effects as transconductance degradation and increased gate capacitance. The device model, which agrees with experimental devices fabricated in this laboratory, is used in the simulation of direct-coupled FET logic (DCFL) inverters with saturated resistor loads. Based on simulation results, the importance of large driver threshold voltage not only for small propagation delay times but for wide logic swings and noise margins is demonstrated. Furthermore, minimum delay times are found to occur at small supply voltages as seen experimentally. Both of these results are attributed to the reduction of detrimental high gate bias effects. The major effect of reducing the gate length on delay time is to decrease the load capacitance of the gate. Using 0.25-µm gates, delay times of 5 and 3.6 ps at 300 and 77 K, respectively, are predicted. Finally, the recently introduced In-GaAs/AlGaAs MODFET's are shown to have switching speeds superior to those of conventional GaAs/AlGaAs MODFET's.     

High performance 0.1 μm gate-length p-type SiGe MODFET's andMOS-MODFET's

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide-semiconductor MODFET (MOS-MODFET) with 0.1 μm gate-length have been fabricated on a high hole mobility SiGe-Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g_m) of 142 mS/mm, a unity current gain cut-off frequency (f_T) of 45 GHz and a maximum oscillation frequency (f_MAX) of 81 GHz, 5 nm-thick high quality jet-vapor-deposited (JVD) SiO₂ was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA/μm at V_gs=6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g _m of 90 mS/mm, f_T of 38 GHz, and f_max of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF_min) of 1.29 dB and an associated power gain (G_a) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF _min of 0.92 dB and a G_a of 12 dB at 2 GHz. These DC, RF, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications     

Application of the Shubnikov-de Haas oscillations in the characterization of Si MOSFET's and GaAs MODFET's

The Shubnikov-de Haas magnetoconductance oscillations were used to measure directly the gate-to-channel capacitance of Si MOSFET's and GaAs MODFET's, to detect the onset of parallel conduction in GaAs MODFET's, and to provide an approximate measure of channel length in sub-100-nm channel of Si MOSFET's. The measurements do not require knowledge of any device parameters, are immune to any gate parasitic capacitance, and are independent of source and drain series resistances. One needs to know only the magnetic field, the oscillation period (for gate-to-channel capacitance measurement), the gate voltage (for detection of the onset of parallel conduction), and the number of oscillation peaks (for the channel length characterization). Experimental results have shown that the characterization methods are accurate, and can be applied to FET's with sub-100-nm channel length.     

The dependence of 77 K electron velocity-field characteristics on low-field mobility in AlGaAs-GaAs modulation-doped structures

We have used the geometrical magnetoresistance method to measure the electron velocities and mobilities as functions of electric field in AlGaAs-GaAs modulation-doped structures at 77 K. These structures had a variety of AlGaAs mole fractions and undoped setback layers resulting in different low-field mobilities in the different structures. We find that higher low-field mobility does not lead to a higher high-field velocity, and in fact, that at electric fields found in operating MODFET's, the mobilities and velocities were about the same in various AIGaAs-GaAs MODFET's. The results indicate that high low-field mobility is not an important parameter for MODFET design and does not even significantly reduce the parasitic source resistance in an operating FET. Furthermore, because of the strong electric field dependence of the mobility, low-field source resistance measurements are not adequate for determining the source resistance in an operating FET.