DC and microwave performance of high-current AlGaN/GaNheterostructure field effect transistors grown on p-type SiC substrates

The fabrication and characterization of high performance AlGaN/GaN heterostructure field effect transistors (HFETs) grown on p-type SiC substrates are reported for the first time. The HFETs were fabricated with gate lengths of 0.25, 0.5, and 1 μm. These devices exhibited simultaneously high drain currents, high extrinsic transconductances, and excellent frequency response. The 0.25-μm gate-length devices produced a peak drain current of 1.43 A/mm, a transconductance of 229 mS/mm, a unity current-gain cutoff frequency of 53 GHz, and a maximum frequency of oscillation of 58 GHz. The unity current-gain cutoff frequency also exhibited little degradation as the drain-source bias was swept up to 20 V. These results represent a significant improvement over similar HFETs grown on sapphire substrates and are attributed to the higher thermal conductivity and reduced lattice mismatch associated with SiC substrates     

Fabrication and characterization of 100-nm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As double-gate HEMTs with two separate gate controls

In this letter, we demonstrate successful operation of 100-nm T-gates double-gate high electron mobility transistors with two separate gate controls (V/sub g1s/ /spl ne/ V/sub g2s/). These devices are fabricated by means of adhesive bonding technique using enzocyclocbutene polymer. The additional gate enables the variation of the threshold voltage V/sub th/ in a wide range from -0.68 to -0.12V while keeping high cutoff frequency f/sub t/ of about 170 GHz and high maximum oscillation frequency f/sub max/ of about 200 GHz. These devices are considered as being very effective for millimeter-wave mixing applications and are promising devices for the fabrication of velocity modulation transistor (VMT) (Sakaki et al., 1982).     

0.15-$muhboxm$-Gate InAlAs/InGaAs/InP E-HEMTs Utilizing Ir/Ti/Pt/Au Gate Structure

High-current 0.15-mum-gate enhancement-mode high-electron mobility transistors utilizing Ir/Ti/Pt/Au gate metallization were fabricated using a new process including a high-temperature gate anneal that is required for Schottky-barrier height enhancement for the Ir-based gate contact. SiN_x encapsulation was employed to prevent thermal degradation of device layer during the high-temperature gate anneal. Excellent enhancement-mode operation, with a threshold voltage of 0.1 V and I_DSS of 2.1 mA/mm, was realized. Both the annealed and unannealed devices exhibited high g_m,max and I_D,max of 800 mS/mm and 430 mA/mm, respectively. A unity current-gain cutoff frequency f_T of 151 GHz and a maximum oscillation frequency f_MAX of 172 GHz were achieved. From the dc and RF characteristics, it can be deduced that there was no degradation of the gate contact and the heterostructure due to gate annealing. Furthermore, it was found that the gate diffusion during gate annealing was negligible since no increase in g_m,max was observed     

Sub-1/4-μm dual-gate CMOS technology using in-situ dopedpolysilicon for nMOS and pMOS gates

A new dual poly-Si gate CMOS fabrication process is proposed. The incorporated technology features a boron-penetration-resistant MBN gate structure for pMOSFET's, and a dual poly-Si gate CMOS process involving separate depositions of in-situ doped n⁺ and p⁺ poly-Si for the nMOS and pMOS gates, 0.2-μm CMOS devices with 3.5-nm gate oxide have been successfully fabricated. The advantages of the new process are demonstrated on these test devices. A CMOS 1/16 dynamic frequency divider fabricated by the new process functions properly up to 5.78 GHz at a 2-V supply voltage     

高阻硅基GaN晶片上MIS栅结构GaN HEMT射频器件研制

5G 通信中3. 4~3. 6 GHz 是主要使用频段。GaN 射频器件由于高频、低功耗、高线性度等优势,满足5G 通信应用需求。文中在高阻硅基GaN 外延片上研制了AlGaN/GaN 高电子迁移率晶体管(High Electron Mobility Transistor, HEMT),并分析了金属鄄绝缘层鄄半导体(Metal-Insulator-Semiconductor,MIS)栅对器件直流和射频特性的影响。研究发现:相比于肖特基栅结构,MIS 栅结构器件栅极泄漏电流减少2~5 个数量级,漏极驱动电流能力和跨导提高10%以上;频率为3. 5 GHz 时,增益从1. 5 dB 提升到4. 0 dB,最大资用增益从5. 2 dB 提升到11. 0 dB,电流增益截止频率为8. 3 GHz,最高振荡频率为10. 0 GHz。     

Quarter-micrometer gate ion-implanted GaAs MESFET's with an f1 of 126 GHz

The fabrication and characterization of a 0.25-μm-gate, ion-implanted GaAs MESFET with a maximum current-gain cutoff frequency f_t of 126 GHz is reported. Extrapolation of current gains from bias-dependent S-parameters at 70-100% of I _dss yields f₁'s of 108-126 GHz. It is projected that an f₁ of 320 GHz is achievable with 0.1-μm-gate GaAs MESFETs. This demonstration of f₁'s over 100 GHz with practical 0.25-μm gate length substantially advances the high-frequency operation limits of short-gate GaAs MESFETs     

Gate length scaling in high performance InGaP/InGaAs/GaAs pHEMTs

The performance of InGaP-based pHEMTs as a function of gate length has been examined experimentally. The direct-current and microwave performance of pHEMTs with gate lengths ranging from 1.0-0.2 μm has been evaluated. Extrinsic transconductances from 341 mS/mm for 1.0 μm gate lengths to 456 mS/mm for 0.5 μm gate lengths were obtained. High-speed device operation has been verified, with f_t of 93 GHz and f_max of 130 GHz for 0.2 μm gate lengths. The dependence of DC and small-signal device parameters on gate length has been examined, and scaling effects in InGaP-based pHEMT's are examined and compared to those for AlGaAs/InGaAs/GaAs pHEMTs. High-field transport in InGaP/InGaAs heterostructures is found to be similar to that of AlGaAs/InGaAs heterostructures. The lower ϵ_r of InGaP relative to AlGaAs is shown to be responsible for the early onset of short-channel effects in InGaP-based devices     

Enhancement-mode AlGaN/GaN HEMTs fabricated by fluorine plasma treatment

The fabrication of enhancement-mode A1GaN/GaN HEMTs by fluorine plasma treatment on sapphire substrates is reported. A new method is used to fabricate devices with different fluorine plasma RF power treatments on one wafer to avoid differences between different wafers. The plasma-treated gate regions of devices treated with different fluorine plasma RF powers were separately opened by a step-and-repeat system. The properties of these devices are compared and analyzed. The devices with 150 W fluorine plasma treatment power and with 0.6μm gate-length exhibited a threshold voltage of 0.57 V, a maximum drain current of 501 mA/mm, a maximumtransconductance of 210 m S/mm, a current gain cutoff frequency of 19.4 GHz and a maximum oscillation frequency of 26 GHz. An excessive fluorine plasma treatment power of 250 W results in a small maximum drain current, which can be attributed to the implantation of fluorine plasma in the channel.     

0.25 μm Self-Aligned AlGaN/GaN High Electron Mobility Transistors

Self-aligned AlGaN/GaN high electron mobility transistors grown on semiinsulating SiC substrates with a 0.25 mum gate-length were fabricated using a single-step ohmic process. Our recently developed Mo/Al/Mo/Au-based ohmic contact requiring annealing temperatures between 500degC and 600degC was utilized. Ohmic contact resistances between 0.35-0.6 Omega ldr mm were achieved. These 0.25 mum gate-length devices exhibited drain current density as high as 1.05 A/mm at a gate bias of 0 V and a drain bias of 10 V. A knee voltage of less than 2 V and a peak extrinsic transconductance (g_m ) of 321 mS/mm were measured. For their microwave characteristics, a unity gain cutoff frequency (f_T ) of 82 GHz and maximum frequency of oscillation (f _max) of 103 GHz were measured.     

Comparison of 80-200 nm gate lengthAl0.25GaAs/GaAs/(GaAs:AlAs), Al0.3GaAs/In0.15GaAs/GaAs, and In0.52AlAs/In0.65GaAs/InPHEMTs

In this paper we present a comparative study of the high frequency performance of 80-200 mm gate length Al_0.25GaAs/GaAs/(GaAs:AlAs) superlattice buffer quantum well (QW) HEMTs, Al_0.3GaAs/In_0.15GaAs/GaAs pseudomorphic HEMTs and In_0.52AlAs/In_0.65GaAs/InP pseudomorphic HEMTs. From an experimental determination of the delays associated with transiting both the intrinsic and parasitic regions of the devices, effective electron velocities in the intrinsic channel region under the gate of the HEMT's were extracted. This analysis showed no evidence of any systematic increase in the effective channel velocity with reducing gate length in any of the devices. The effective electron velocity in the channel of the pseudomorphic In_0.65GaAs/InP HEMTs, determined to be at least 2.5×10⁵, was was around twice that of either the Al_0.25GaAs/GaAs quantum well or pseudomorphic In_0.15GaAs/GaAs HEMTs, resulting in 80 nm gate length devices with f_T's of up to 275 GHz. We also show that device output conductance is strongly material dependent. A comparison of the different buffer layers showed that the (GaAs:AlAs) superlattice buffer was most effective in confining electrons to the channel of the Al_0.25GaAs/GaAs HEMTs, even for 80 nm gate length devices. We propose this may be partly due to the presence of minigaps in the superlattice which provide a barrier to electrons with energies of up to 0.6 eV. The output conductance of pseudomorphic In_0.65GaAs/InP HEMTs was found to be inferior to the GaAs based devices as carriers in the channel have greater energy due to their higher effective velocity and so are more difficult to confine to the 2DEG     

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.     

AlGaN/GaN HEMTs on a (001)-Oriented Silicon Substrate Based on 100-nm SiN Recessed Gate Technology for Microwave Power Amplification

AlGaN/GaN high-electron mobility transistors on (001)-oriented silicon substrates with a 0.1-mum gamma-shaped gate length are fabricated. The gate technology is based on a silicon nitride (SiN) thin film and uses a digital etching technique to perform the recess through the SiN mask. An output current density of 420 mA/mm and an extrinsic transconductance g_m of 228 mS/mm are measured on 300-mum gate-periphery devices. An extrinsic cutoff frequency f_t of 28 GHz and a maximum oscillation frequency f_max of 46 GHz are deduced from S-parameter measurements. At 2.15 GHz, an output power density of 1 W/mm that is associated to a power-added efficiency of 17% and a linear gain of 24 dB are achieved at V_DS = 30 V and V_GS = -1.2 V.     

Ion-implanted GaAs/AlGaAs heterojunction FET's grown by MOCVD

The successful fabrication of an ion-implanted GaAs/AlGaAs heterojunction FET device is discussed. Half-micrometer gate-length FET devices are fabricated by ion implantation into GaAs/AlGa heterostructures grown by metalorganic chemical vapor deposition (MOCVD) on 3-in-diameter GaAs substrates. The FET device exhibits a maximum extrinsic transconductance of 280 mS/mm with reduced transconductance variation over 2 V of gate bias. Excellent microwave performance is achieved with an f_t of 40 GHz, which is comparable to results obtained from 0.25-μm gate GaAs MESFETs. The effects of ion implantation on the heterojunction and corresponding device characteristics are also discussed     

Silicon Oxide enhanced Schottky gate In0.53Ga0.47As FET's with a self-aligned recessed gate structure

We present the fabrication and characterization of an In0.53Ga0.47As enhanced Schottky gate FET with a self-aligned recessed gate structure. A thin layer of e-beam evaporated silicon oxide was used to reduce the gate leakage current. For a n-channel doping of 8 × 10¹⁶cm^-3and a gate length of 1.5 µm, these devices showed good pinchoff characteristics with transconductances of 150 mS/mm. The effective velocity of electrons at current saturation is deduced to be 2.4 × 10⁷cm/s at the drain end of the gate. At 3 GHz these devices have a maximum available gain of 10 dB, decreasing to 6 dB at 6 GHz.     

InP-based enhancement-mode pseudomorphic HEMT with strainedIn0.45Al0.55As barrier andIn0.75Ga0.25As channel layers

Using strained aluminum-rich In_0.45Al_0.55As as Schottky contact materials to enhance the barrier height and indium-rich In_0.75Ga_0.25As as channel material to enhance the channel performance, we have developed InP-based enhancement-mode pseudomorphic InAlAs/InGaAs high electron mobility transistors (E-PHEMT's) with threshold voltage of about 170 mv. A maximum extrinsic transconductance of 675 mS/mm and output conductance of 15 mS/mm are measured respectively at room temperature for 1 μm-gate-length devices, with an associated maximum drain current density of 420 mA/mm at gate voltage of 0.9 V. The devices also show excellent rf performance with cutoff frequency of 55 GHz and maximum oscillation frequency of 62 GHz. To the best of the authors' knowledge, this is the first time that InP-based E-PHEMT's with strained InAlAs barrier layer have been demonstrated     

Ultra-high-speed digital circuit performance in 0.2-μmgate-length AlInAs/GaInAs HEMT technology

The fabrication of fifteen-stage ring oscillators and static flip-flop frequency dividers with 0.2-μm gate-length AlInAs/GaInAs HEMT technology is described. The fabricated HEMT devices within the circuits demonstrated a g_m transconductance of 750 mS/mm and a full-channel current of 850 mA/mm. The measured cutoff frequency of the device is 120 GHz. The shortest gate delay measured for buffered-FET-logic (BFL) ring oscillators at 300 K was 9.3 ps at 66.7 mW/gate (fan-out=1); fan-out sensitivity was 1.5 ps per fanout. The shortest gate delay measured for capacitively enhanced logic (CEL) ring oscillators at 300 K was 6.0 ps at 23.8 mW/gate (fan-out=1) with a fan-out sensitivity of 2.7 ps per fan-out. The CEL gate delay reduced to less than 5.0 ps with 11.35-mW power dissipation when measured at 77 K. The highest operating frequency for the static dividers was 26.7 GHz at 73.1 mW and 300 K     

AlGaN/GaN HEMTs on SiC with f/sub T/ of over 120 GHz

AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with a 0.12 /spl mu/m gate length have been fabricated. These 0.12-/spl mu/m gate-length devices exhibited maximum drain current density as high as 1.23 A/mm and peak extrinsic transconductance of 314 mS/mm. The threshold voltage was -5.2 V. A unity current gain cutoff frequency (f/sub T/) of 121 GHz and maximum frequency of oscillation (f/sub max/) of 162 GHz were measured on these devices. These f/sub T/ and f/sub max/ values are the highest ever reported values for GaN-based HEMTs.     

High-performance E-mode AlGaN/GaN HEMTs

Enhancement-mode AlGaN/GaN high electron-mobility transistors have been fabricated with a gate length of 160 nm. The use of gate recess combined with a fluorine-based surface treatment under the gate produced devices with a threshold voltage of +0.1 V. The combination of very high transconductance (> 400 mS/mm) and low gate leakage allows unprecedented output current levels in excess of 1.2 A/mm. The small signal performance of these enhancement-mode devices shows a record current cutoff frequency (f/sub T/) of 85 GHz and a power gain cutoff frequency (f/sub max/) of 150 GHz.     

超薄势垒InAlN/GaN HFET器件高频特性分析

采用二次外延重掺杂n+ GaN实现非合金欧姆接触,并通过优化干法刻蚀和金属有机化学气相沉积(MOCVD)外延工艺,有效降低了欧姆接触电阻.将非合金欧姆接触工艺应用于InAlN/GaN异质结场效应晶体管(HFET)器件制备,器件的有效源漏间距缩小至600 nm.同时,结合40 nm T型栅工艺,制备了高电流截止频率(fT)和最大振荡频率(fmax)的InAlN/GaN HFET器件.结果显示减小欧姆接触电阻和栅长后,器件的电学特性,尤其是射频特性得到大幅提升.栅偏压为0V时,器件最大漏源饱和电流密度达到1.88 A/mm;直流峰值跨导达到681 mS/mm.根据射频小信号测试结果外推得到器件的fT和fmax同为217 GHz.     

120-nm gate-length In0.7Ga0.3As/In0.52Al0.48As InP-based HEMT

120 nm gate-length In_(0.7)Ga_(0.3)As/In_(0.52)Al_(0.48) As InP-based high electron mobility transitions(HEMTs) are fabricated by a new T-shaped gate electron beam lithograph(EBL) technology,which is achieved by the use of a PMMA/PMGI/ZEP520/PMGI four-layer photoresistor stack.These devices also demonstrate excellent DC and RF characteristics:the transconductance,maximum saturation drain-to-source current,threshold voltage,maximum current gain frequency,and maximum power-gain cutoff frequency of InGaAs/I...