Two-dimensional electron gas characteristics of InP-based high electron mobility transistor terahertz detector

The samples of InxGa（1-x）As/In（0.52）Al（0.48）As two-dimensional electron gas（2DEG）are grown by molecular beam epitaxy（MBE）.In the sample preparation process,the In content and spacer layer thickness are changed and two kinds of methods,i.e.,contrast body doping andδ-doping are used.The samples are analyzed by the Hall measurements at 300 Kand 77 K.The InxGa1-xAs/In0.52Al0.48As 2DEG channel structures with mobilities as high as 10289 cm^2/V·s（300 K）and42040 cm^2/V·s（77 K）are obtained,and the values of carrier concentration（Nc）are 3.465×10^12/cm^2 and 2.502×10^12/cm^2,respectively.The THz response rates of In P-based high electron mobility transistor（HEMT）structures with different gate lengths at 300 K and 77 K temperatures are calculated based on the shallow water wave instability theory.The results provide a reference for the research and preparation of In P-based HEMT THz detectors.

Influence of a two-dimensional electron gas on current-voltage characteristics of Al_(0.3)Ga_(0.7) N/GaN high electron mobility transistors

The J-V characteristics of AltGa1 tN/GaN high electron mobility transistors（HEMTs） are investigated and simulated using the self-consistent solution of the Schro dinger and Poisson equations for a two-dimensional electron gas（2DEG） in a triangular potential well with the Al mole fraction t = 0.3 as an example.Using a simple analytical model,the electronic drift velocity in a 2DEG channel is obtained.It is found that the current density through the 2DEG channel is on the order of 10^13 A/m^2 within a very narrow region（about 5 nm）.For a current density of 7 × 10^13 A/m62 passing through the 2DEG channel with a 2DEG density of above 1.2 × 10^17 m^-2 under a drain voltage Vds = 1.5 V at room temperature,the barrier thickness Lb should be more than 10 nm and the gate bias must be higher than 2 V.

Effects of Si δ-Doping Condition and Growth Interruption on Electrical Properties of InP-Based High Electron Mobility Transistor Structures

The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.

1.0μm gate-length InP-based InGaAs high electron mobility transistors by mental organic chemical vapor deposition

InGaAs high electron mobility transistors （HEMTs） on InP substrate with very good device performance have been grown by mental organic chemical vapor deposition （MOCVD）. Room temperature Hall mobilities of the 2-DEG are measured to be over 8 700 cm^2/V-s with sheet carrier densities larger than 4.6× 10^12 cm^ 2. Transistors with 1.0 μm gate length exhibits transconductance up to 842 mS/ram. Excellent depletion-mode operation, with a threshold voltage of-0.3 V and IDss of 673 mA/mm, is realized. The non-alloyed ohmic contact special resistance is as low as 1.66×10^-8 Ω/cm^2, which is so far the lowest ohmic contact special resistance. The unity current gain cut off frequency （fT） and the maximum oscillation frequency （fmax） are 42.7 and 61.3 GHz, respectively. These results are very encouraging toward manufacturing InP-based HEMT by MOCVD.

Effect of defects properties on InP-based high electron mobility transistors

The performance damage mechanism of InP-based high electron mobility transistors(HEMTs) after proton irradiation has been investigated comprehensively through induced defects.The effects of the defect type, defect energy level with respect to conduction band ET, and defect concentration on the transfer and output characteristics of the device are discussed based on hydrodynamic model and Shockley–Read–Hall recombination model.The results indicate that only acceptorlike defects have a significant influence on device operation.Meanwhile, as defect energy level ETshifts away from conduction band, the drain current decreases gradually and finally reaches a saturation value with ETabove 0.5 eV.This can be attributed to the fact that at sufficient deep level, acceptor-type defects could not be ionized any more.Additionally,the drain current and transconductance degrade more severely with larger acceptor concentration.These changes of the electrical characteristics with proton radiation could be accounted for by the electron density reduction in the channel region from induced acceptor-like defects.

Enhancement of terahertz coupling efficiency by improved antenna design in GaN/AlGaN high electron mobility transistor detectors

An optimized micro-gated terahertz detector with novel triple resonant antenna is presented.The novel resonant antenna operates at room temperature and shows more than a 700% increase in photocurrent response compared to the conventional bowtie antenna.In finite-difference-time-domain simulations,we found the performance of the self-mixing GaN/AlGaN high electron mobility transistor detector is mainly dependent on the parameters L gs（the gap between the gate and the source/drain antenna） and L w（the gap between the source and drain antenna）.With the improved triple resonant antenna,an optimized micrometer-sized AlGaN/GaN high electron mobility transistor detector can achieve a high responsivity of 9.45×102 V/W at a frequency of 903 GHz at room temperature.

Breakdown voltage analysis of Al_(0.25)Ga_(0.75)N/GaN high electron mobility transistors with partial silicon doping in the AlGaN layer

In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.

Electric field driven plasmon dispersion in AlGaN/GaN high electron mobility transistors

We present a theoretical study on the electric field driven plasmon dispersion of the two-dimensional electron gas （2DEG） in A1GaN/GaN high electron mobility transistors （HEMTs）. By introducing a drifted Fermi-Dirac distribution, we calculate the transport properties of the 2DEG in the A1GaN/GaN interface by employing the balance-equation approach based on the Boltzmann equation. Then, the nonequilibrium Fermi-Dirac function is obtained by applying the calculated electron drift velocity and electron temperature. Under random phase approximation （RPA）, the electric field driven plas- mon dispersion is investigated. The calculated results indicate that the plasmon frequency is dominated by both the electric field E and the angle between wavevector q and electric field E. Importantly, the plasmon frequency could be tuned by the applied source-drain bias voltage besides the gate voltage （change of the electron density）.

Formation of two-dimensional electron gas at AlGaN/GaN heterostructure and the derivation of its sheet density expression

Models for calculating the sheet densities of two-dimensional electron gas （2DEG） induced by spontaneous and piezoelectric polarization in A1GaN/GaN, A1GaN/A1N/GaN, and GaN/A1GaN/GaN heterostructures are provided. The detailed derivation process of the expression of 2DEG sheet density is given. A longstanding confusion in a very widely cited formula is pointed out and its correct expression is analyzed in detail.

Electron mobility in the linear region of an AlGaN/AlN/GaN heterostructure field-effect transistor

We simulate the current-voltage （I-V） characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors （HFETs） with different gate lengths using the quasi-two-dimensional （quasi-2D） model. The calculation results obtained using the modified mobility model are found to accord well with the experimental data. By analyzing the variation of the electron mobility for the two-dimensional electron gas （213EG） with the electric field in the linear region of the AlGaN/AlN/GaN HFET I-V output characteristics, it is found that the polarization Coulomb field scattering still plays an important role in the electron mobility of AlGaN/AlN/GaN HFETs at the higher drain voltage and channel electric field. As drain voltage and channel electric field increase, the 2DEG density reduces and the polarization Coulomb field scattering increases, as a result, the 2DEG electron mobility decreases.

Growth condition optimization and mobility enhancement through inserting AlAs monolayer in the InP-based In_xGa_(1-x)As/In_(0.52)Al_(0.48)As HEMT structures

The structure of In P-based In_xGa_（1-x） As/In0.52Al0.48 As pseudomorphic high electron mobility transistor（PHEMT）was optimized in detail.Effects of growth temperature,growth interruption time,Si δ-doping condition,channel thickness and In content,and inserted Al As monolayer（ML） on the two-dimensional electron gas（2DEG） performance were investigated carefully.It was found that the use of the inserted Al As monolayer has an enhancement effect on the mobility due to the reduction of interface roughness and the suppression of Si movement.With optimization of the growth parameters,the structures composed of a 10 nm thick In0.75Ga0.25 As channel layer and a 3 nm thick Al As/In0.52Al0.48 As superlattices spacer layer exhibited electron mobilities as high as 12500 cm^2·V-1·s^（-1）（300 K） and 53500 cm^2·V~（-1_·s^（-1）（77 K） and the corresponding sheet carrier concentrations（Ns） of 2.8×10^（12）cm^（-2）and 2.9×1012cm^（-2）,respectively.To the best of the authors＇ knowledge,this is the highest reported room temperature mobility for In P-based HEMTs with a spacer of 3 nm to date.

基于101.6 mm晶圆35 nm InP HEMT工艺的340 GHz低噪声放大器芯片研制

实现了在101.6 mm InP晶圆上制备35 nm的增强型InP高电子迁移率晶体管。通过InAs复合沟道外延结构设计,使得室温二维电子气迁移率面密度乘积达到4.2×10^(16)/(V·s)。采用了铂钛铂金埋栅工艺技术,典型器件最大跨导达到2900 mS/mm,电流增益截止频率达到460 GHz,最高振荡频率为720 GHz。同时研制出340 GHz低噪声放大器芯片,在310~350 GHz内小信号增益22~27 dB,噪声系数在8 dB以下。建立了340 GHz InP低噪声放大器芯片技术平台,为太赫兹低噪声单片微波集成电路的发展奠定基础。

Growth condition optimization and mobility enhancement through prolonging the GaN nuclei coalescence process of AlGaN/AlN/GaN structure

AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas（2DEG） performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.

Heterojunction-engineered carrier transport in elevated-metal metal-oxide thin-film transistors

This study investigates the carrier transport of heterojunction channel in oxide semiconductor thin-film transistor(TFT)using the elevated-metal metal-oxide(EMMO)architecture and indium−zinc oxide(InZnO).The heterojunction band diagram of InZnO bilayer was modified by the cation composition to form the two-dimensional electron gas(2DEG)at the interface quantum well,as verified using a metal−insulator−semiconductor(MIS)device.Although the 2DEG indeed contributes to a higher mobility than the monolayer channel,the competition and cooperation between the gate field and the built-in field strongly affect such mobility-boosting effect,originating from the carrier inelastic collision at the heterojunction interface and the gate field-induced suppression of quantum well.Benefited from the proper energy-band engineering,a high mobility of 84.3 cm2·V^(−1)·s^(−1),a decent threshold voltage(V_(th))of−6.5 V,and a steep subthreshold swing(SS)of 0.29 V/dec were obtained in InZnO-based heterojunction TFT.

基于InP HEMT的太赫兹分谐波混频器芯片设计

基于70 nm InP高电子迁移率晶体管(HEMT)工艺,研制了一款175~205 GHz分谐波混频器太赫兹单片集成电路(TMIC)。使用三线耦合Marchand巴伦实现本振信号的平衡-不平衡转换。在射频端口设计了紧凑型耦合线结构的带通滤波器,实现对射频信号低损耗带通传输的同时缩小了芯片尺寸。测试结果表明混频器在175~205 GHz频率范围内,单边带(SSB)变频损耗小于15 dB,典型值14 dB。混频器中频频带为DC~25 GHz,射频端口对本振二次谐波信号的隔离度大于20 dB。芯片尺寸为1.40 mm×0.97 mm,能够与相同工艺的功率放大器、低噪声放大器实现片上集成,从而满足太赫兹通信等不同领域的应用需求。

基于InP基HEMT器件的D波段倍频源设计

传统太赫兹倍频源多采用混合集成电路的实现方式,导致太赫兹倍频源存在体积大、封装损耗高、稳定性差等问题。采用栅长2×25μm的磷化铟(InP)基高电子迁移率晶体管(HEMT)有源器件,利用先进系统设计(ADS)原理仿真和电磁仿真(EM)联合仿真分析的方法设计了一款全单片集成的D波段倍频源。该倍频源采用倍频+放大的形式设计实现,其中第一级为二倍频电路,第二级采用放大电路。在132~154 GHz范围内,当输入功率为4.5 dBm时,输出功率大于6 dBm,基波抑制比优于31 dBc,三次谐波抑制比优于36 dBc,最大输出功率为9 dBm@144 GHz,对应的变频增益为4.5 dB,该倍频源的芯片面积约为3.1 mm×1.3 mm。该设计为全单片集成的太赫兹源和实现小型化太赫兹源提供了新的选项。

基于InP基HEMTs的W波段高增益低噪声放大MMIC（英文）

基于自主研发的InP基高电子迁移率晶体管工艺设计并制作了一款W波段单级低噪声放大单片毫米波集成电路.共源共栅拓扑结构和共面波导工艺保证了该低噪声放大器紧凑的面积和高的增益,其芯片面积为900μm×975μm,84~100 GHz频率范围内增益大于10 dB,95 GHz处小信号增益达到最大值为15.2dB.根据调查对比,该单级放大电路芯片具有最高的单级增益和相对高的增益面积比.另外,该放大电路芯片在87.5 GHz处噪声系数为4.3 dB,88.8 GHz处饱和输出功率为8.03 dBm.该低噪声放大器芯片的成功研制对于构建一个W波段信号接收前端具有重要的借鉴意义.

Lattice-Matched InP-Based HEMTs with T^T of 120GHz

Lattice matched InP based InAlAs/InGaAs HEMTs with 120GHz cutoff frequency are reported.These devices demonstrate excellent DC characteristics:the extrinsic transconductance of 600mS/mm,the threshold voltage of -1 2V,and the maximum current density of 500mA/mm.

基于Ti/Pt/Au欧姆接触金属系统的InP基HEMT器件

应用钛/铂/金(Ti/Pt/Au)金属系统在InP基HEMT制备工艺中形成了良好的欧姆接触,通过优化合金条件,获得了较低的欧姆接触电阻,并在此基础上对钛/铂/金欧姆接触形成机理进行了深入讨论。实验结果表明:在氮气气氛下进行温度300℃/30 s快速热退火后,得到欧姆接触最小电阻值为0.025Ω·mm。同时合金界面形态良好。制备出栅长1.0μm的InP基HEMT器件,测试结果表明器件具有良好的DC和RF特性,器件最大跨导(Gmmax)为672 mS/mm。饱和源漏电流IDSS为900 mA/mm,阈值电压为-0.8 V,单一的电流增益截止频率(fT)为40 GHz,最大晶振fmax为45 GHz。

THz InP HEMT和HBT技术的最新研究进展

概述了太赫兹（THz）InP技术的优势、应用前景及美国的发展规划。重点对国外THzInP高电子迁移率晶体管（HEMT）和异质结双极晶体管（HBT）的技术进展和突破进行了详细阐述，其中国外HEMT和HBT器件的工作频率都达到了1THZ以上，国外报道的650GHz以上的InP太赫兹单片集成电路（TMIC）很多，包括低噪声放大器和功率放大器等，并且性能优异。介绍了我国THzInP技术的研究现状，国内InPHEMT和HBT器件的工作频率最高可达600GHz，电路的工作频率在300GHZ左右。最后，对国内外的最新技术水平进行了对比，并在对比的基础上针对存在的问题提出了我国在THzInP领域的发展建议。