一种预计低噪声GaAs MESFET噪声系数的方法

本文提出了一种预计低噪声GaAs MESFET噪声系数的简便方法.此法只要精确测量器件的总栅源电容C_(gs)、本征跨导gm和总夹断电压W_p,就能求出器件的栅长L、有源层载流子浓度N和厚度a,进而可以预计器件的最小噪声系数NF_(min),故简称为CGW方法.文中还引进了相关栅长L_a的概念,用L_a、N和a预计器件的最小噪声系数与实测值更相符合.本方法还可以具体分析栅长、寄生电阻和GaAs材料质量等因素对器件噪声系数的影响,以便及时调整有关参数,改善器件性能.     

4GHz低噪声GaAs MESFET参数研究

本文论述4GHz低噪声GaAs MESFET在缩短栅长L,减小寄生电阻(R_s+R_g)的同时需减小等效噪声电阻R_n,以获得较理想的增益和噪声性能.本文还叙述了器件主要参数的控制,并指出在亚微米栅长时栅边缘效应对器件噪声系数的影响.     

12GHz 1.5dB亚微米栅GsAs MESFET

<正> 南京固体器件研究所成功地研制了深槽亚微米栅GaAs MESFET。器件栅工0.4～0.6μm、栅宽150μm、槽深0.3～0.4μm。以1.8×1.8mm标准陶瓷金属微带管壳封装,进一步改善了射频特性。在12GHz下测量,器件噪声系数的最佳值为1.4dB,相关增益7.5dB。大部分器件的噪声系数在1.5～3.5dB范围内。器件在2～12GHz频率范围内的s参数也较好。与日本三菱公司的2SK267和NEC的NE38883 MESFET 进行了同等条件下测试对比,说明测试结果可靠。 用于制作器件的GaAs材料的质量较好。GaAs半绝缘衬底有较高的电阻率;缓冲层纯度较高,提高了与有源层交界面附近的迁移率;有源层为N~+-N层,有利于减小源漏接触电阻。这些为器件获得高增益、低噪声打下了良好的基础。     

超低噪声毫米波PHEMT

以AlGaAs/InGaAs/GaAs为基础的十分之一微米栅长PHEMT器件在43GHz下提供了最优良的低噪声性能。测量的室温器件噪声系数为1.32dB(噪声温度=103K),相关增益6.7dB,在17K物理温度下,噪声系数为0.36dB(噪声温度=25K),相关增益为6.9dB,这是目前报道的43GHz下GaAs基器件的最低噪声系数。     

低噪声高电子迁移率晶体管

采用直接描绘电子束刻蚀法制造了用于低噪声极高频(EHF)放大器的亚半微米栅长的高电子迁移率晶体管。调制掺杂的外延结构是用分子束外延法生长的,在10~(12)电子/cm~2的电子浓度时,室温下的霍耳迁移率为8000cm~2/V·sec,液氮温度下为77,600cm~2/V·sec。通过腐蚀通n~+GaAs接触层的凹楷的方法确定了窄达0.28μm的栅长。0.4μm栅长的耗尽型器件的直流跨导超过260mS/mm。对0.37μm栅长的器件,进行了噪声系数和相关增益的测量,在34GHz下,得到了2.7dB的噪声系数和5.9dB的相关增益。还制造了具有240mS/mm跨导的增强型器件,对0.35μm的栅长,在18GHz下,它们的噪声系数为1.5dB,相关增益为10.5dB。这些结果可以和已报导过的最好的0.25μm栅长的GaAsMESFET的噪声系数相匹敌。     

X波段噪声系数1.4分贝的GaAs MESFET

<正>南京固体器件研究所已研制成功栅长0.5μm、栅宽280μm,以φ2mm陶瓷金属微带管壳封装的实用化的GaAs MESFET.在9.5GHz下测得最佳水平器件的噪声系数为1.4dB,相关增益大于7dB.大部分器件的噪声系数在1.5～2.5dB范围内.与日本NEC的NE388MESFET进行同等条件下测试对比,说明测试结果可靠.     

MBE生长的高性能MDAlGaAs/GaAs结构材料

本文报道了用国产MBE装置和源材料生长调制掺杂(MD)AlGaAs/GaAs结构材料,用霍耳效应、光荧光测量材料的电学和光学性能,用电化学C-V检测分布特性,用电光检测法评估材料的均匀性。用该材料研制栅长0.5μm的HEMT器件,其跨导为200mS/mm,12GHz下的噪声系数达到0.76dB,相关增益6.5dB。     

0.15μm Y型栅高In沟道GaAs PHEMT低噪声器件设计

设计了一种GaAs PHEMT低噪声器件。通过电子束直写手段实现了0.15μm Y型栅,对栅型优化以减小器件栅电阻和栅寄生电容。采用高In含量的沟道设计以改善沟道电子输运特性,采用InGaAs/GaAs复合帽层以改善欧姆接触特性,并通过低噪声工艺流程制作了4×50μm GaAs PHEMT器件。测试结果表明,器件fT达到80GHz,在10GHz处最小噪声系数小于0.4dB,相关增益大于10dB。对于0.15μm栅长GaAs PHEMT器件来说,这是很好的结果。     

采用离子注入MOCVD缓冲层制作的MESFET

采用离子注入的金属有机化学汽相淀积(MOCVD)缓冲层制作了低噪声GaAs金属-半导体场效应晶体管(MESFET)。在12GHz下,0.5μm(栅长)×300μm(栅宽)的FET器件的噪声系数可达1.46dB,相关增益达到10.20dB。此结果证明,采用离子注入MOCVD缓冲层能制成极好的GaAs LNFET,它可以与采用AsCl_3汽相外延和分子束外延制作的类似器件所得的最佳结果相比拟。     

调制掺杂AlGaAs/InGaAs/GaAs应变量子阱结构的研究

报道调制掺杂AlGaAs/InGaAs/GaAs应变量子阱结构的分子束外延生长、变温霍尔效应和电化学c—v测量,并对输运性质进行了讨论。用这种材料研制的PM-HEMT(pseudomorphic high electron mobility transistors)器件,栅长0.4μm,在12GHz下噪声系数1.03dB,相关增益7.5dB。     

GaAs MESFET's by molecular beam epitaxy

The noise performance of "T" shaped Ti/W/Au gate GaAs Schottky-barrier field-effect transistors fabricated on channel layers grown by molecular-beam epitaxy (MBE) is reported. The nominal gate length was about 0.7 µm with a total gate width of 250 µm. Typical noise figure and the associated gain were 1.2 and 14 dB at 4 GHz, and 1.9 and 8.5 dB at 12 GHz. To out knowledge these are the best results reported to date on devices fabricated using MBE-grown GaAs. These preliminary results show the promise of MBE for high-quality GaAs FET's.     

High microwave and ultra-low noise performance of fullyion-implanted GaAs MESFETs with Au/WSiN T-shaped gate

Fully ion-implanted n⁺ self-aligned GaAs MESFETs with high microwave and ultra-low-noise performance have been fabricated. T-shaped gate structures composed of Au/WSiN are employed to reduce gate resistance effectively. A very thin and high-quality channel with high carrier concentration can be formed by adopting the optimum annealing temperature for the channel, and the channel surface suffers almost no damage by using ECR plasma RIE for gate formation. GaAs MESFETs with a gate length as short as 0.35 μm demonstrated a maximum oscillation frequency of 76 GHz. At an operating frequency of 18 GHz, a minimum noise figure of 0.81 dB with an associated gain of 7.7 dB is obtained. A K_f factor of 1.4 estimated by Fukui's noise figure equation, which is comparable to those of AlGaAs/GaAs HEMTs with the same geometry, reveals that the quality of the channel is very high     

Low-noise HEMT using MOCVD

Low-noise HEMT AlGaAs/GaAs heterostructure devices have been developed using metal organic chemical vapor deposition (MOCVD). The HEMT's with 0.5-µm-long and 200-µm-wide gates have shown a minimum noise figure of 0.83 dB with an associated gain of 12.5 dB at 12 GHz at room temperature. Measurements have confirmed calculations on the effect of the number of gate bonding pads On the noise figure for different gate Widths. Substantial noise figure improvement was observed Under low-temperature operation, especially compared to conventional GaAs MESFET's. A two-stage amplifier designed for DBS reception using the HEMT in the first stage has displayed a noise figure under 2.0 dB from 11.7 to 12.2 GHz.     

Comparison of GaAs MESFET noise figures

A method of comparing noise figures of GaAs MESFET's is presented. The noise measure M graphed against gate length for devices having the lowest value of M gives a figure of merit graph against which other devices may be compared. This is useful in determining the relative value of material and process, improvements for a given gate length.     

Microwave performance of 0.25-µm gate length high electron mobility transistors

The performance of 0.25-µm gate length high electron mobility transistors (HEMT's) is reported. Devices were fabricated on layers grown by MBE. One of the heterostructures had no undoped AlGaAS spacer layer (wafer A), whereas the other had a 40-Å spacer layer (wafer B). The maximum stable gain on both wafers was ∼ 12 dB at 18 GHz. The minimum noise figure measured was 0.60 dB at 8 GHz and 1.3 dB at 18 GHz. Wafer A yielded devices with a unity current gain cutoff frequency ftof 65 GHz whereas wafer B gave an ftof 70 GHz. These results can be attributed primarily to the high quality material, low parasitic resistance, and short gate length.     

A new low-noise AlGaAs/GaAs 2DEG FET with a surface undoped layer

A high-performance N-AlGaAs/GaAs selectively doped two-dimensional electron gas (2DEG) FET with a surface undoped layer has been designed and demonstrated. Simple analysis based on the short-channel approximation revealed that an increase in a total layer thickness between a gate electrode and 2DEG at a hetero-interface results in a higher cutoff frequency and a lower noise figure than conventional 2DEG FET's. This is because the gate capacitance can be markedly reduced without a significant decrease in the transconductance owing to a parasitic source resistance. The surface undoped layer intentionally employed in this work can permit the total layer thickness to increase, i.e., the gate capacitance to reduce, without changes in the 2DEG density and in the source resistance. This structure also gives high gate breakdown voltage because of a small neutral region in n- (AlGa)As and a low surface electron field, which possibly yields excellent performance 2DEG FET's for practical use. Fabricated (AlGa)As/ GaAs 2DEG FET's exhibited noticeable room-temperature performances of 0.95-dB noise figure with 10.3-dB associated gain at 12- and 45-GHz cutoff frequency. These are the best data ever reported for 0.5-µm gate length FET's.     

Optimal noise figure of microwave GaAs MESFET's

The optimal value of the minimum noise figure Foof GaAs MESFET's is expressed in terms of either representative equivalent circuit elements or geometrical and material parameters in simple analytical forms. These expressions are derived on a semiempirical basis. The predicted values of Fofor sample GaAs MESFET's using these expressions are in good agreement with the measured values at microwave frequencies. The expressions are then applied to show design optimization for low-noise devices. This exercise indicates that shortening the gate length and minimizing the parasitic gate and source resistances are essential to lower Fo. Moreover, a simple shortening of the gate length may not bring an improved Founless the unit gate width is accordingly narrowed. The maximum value of the unit gate width is defined as the width above which the gate metallization resistance becomes greater than the source series resistance. Short-gate GaAs MESFET's with optimized designs promise a superior noise performance at microwave frequencies throughKband. The predicted values of Foat 20 GHz, for example, for a half-micrometer gate device and a quarter-micrometer gate device are 3 and 2 dB, respectively. These devices could be fabricated with the current technology.     

InGaAs／GaAs异质结构材料及器件应用

概述了ＩｎＧａＡｓ／ＧａＡｓ异质结构材料用于制作微波器件的优越性，叙述了材料的ＭＢＥ生长、输运特性和掺杂分布，以及用于制作Ｋｕ波段低噪声高增益ＨＦＥＴ的结果：栅长０．５μｍ，１２ＧＨｚ下噪声系数０．９３ｄＢ，相关增益９ｄＢ。