Low-power performance of 0.5-μm JFET for low-cost MMIC's inpersonal communications

The low-power microwave performance of an enhancement-mode ion-implanted GaAs JFET is reported. A 0.5-μm×100-μm E-JFET with a threshold voltage of V_th=0.3 V achieved a maximum DC transconductance of g_m=489 mS/mm at V _ds=1.5 V and I_ds=18 mA. Operating at 0.5 mW of power with V_ds=0.5 V and I_ds =1 mA, the best device on a 3-in wafer achieved a noise figure of 0.8 dB with an associated gain of 9.6 dB measured at 4 GHz. Across a 3-in wafer the average noise figure was F_min=1.2 dB and the average associated gain was G_a=9.8 dB for 15 devices measured. These results demonstrate that the E-JFET is an excellent choice for low-power personal communication applications     

Enhancement-Mode GaAs n-Channel MOSFET

This letter introduces the first enhancement-mode GaAs n-channel MOSFETs with a high channel mobility and an unpinned Fermi level at the oxide/GaAs interface. The NMOSFETs feature an In_0.3Ga_0.7 As channel layer, a channel mobility of up to 6207 cm²/Vmiddots, and a dielectric stack thickness of 13.1-18.7 nm. Enhancement-mode NMOSFETs with a gate length of 1 mum, a source/drain spacing of 3 mum, and a threshold voltage of 0.05 V show a saturation current, transconductance, on-resistance, and subthreshold swing of 243 mA/mm, 81 mS/mm, 8.0 Omegamiddotmm, and 162 mV/dec, respectively     

Ultrathin InAlN/AlN Barrier HEMT With High Performance in Normally Off Operation

We present GaN-based high electron mobility transistors (HEMTs) with a 2-nm-thin InAlN/AlN barrier capped with highly doped n⁺⁺ GaN. Selective etching of the cap layer results in a well-controllable ultrathin barrier enhancement-mode device with a threshold voltage of +0.7 V. The n⁺⁺ GaN layer provides a 290-Omega/square sheet resistance in the HEMT access region and eliminates current dispersion measured by pulsed IV without requiring additional surface passivation. Devices with a gate length of 0.5-mum exhibit maximum drain current of 800 mA/mm, maximum transconductance of 400 mS/mm, and current cutoff frequency fT of 33.7 GHz. In addition, we demonstrate depletion-mode devices on the same wafer, opening up perspectives for reproducible high-performance InAlN-based digital integrated circuits.     

Epitaxially-grown GaN junction field effect transistors

Junction field effect transistors (JFETs) are fabricated on a GaN epitaxial structure grown by metal organic chemical vapor deposition (MOCVD). The dc and microwave characteristics of the device are presented. A junction breakdown voltage of 56 V is obtained corresponding to the theoretical limit of the breakdown field in GaN for the doping levels used. A maximum extrinsic transconductance (g_m ) of 48 mS/mm and a maximum source-drain current of 270 mA/mm are achieved on a 0.8 μm gate JFET device at V_GS=1 V and V_DS=15 V. The intrinsic transconductance, calculated from the measured g_m and the source series resistance, is 81 mS/mm. The f_T and f_max for these devices are 6 GHz and 12 GHz, respectively. These JFET's exhibit a significant current reduction after a high drain bias is applied, which is attributed to a partially depleted channel caused by trapped hot-electrons in the semi-insulating GaN buffer layer. A theoretical model describing the current collapse is presented, and an estimate for the length of the trapped electron region is given     

Multiple-channel GaAs/AlGaAs high electron mobility transistors

Multiple-channel high electron mobility transistors (HEMT's) have been designed and fabricated on GaAs/AlGaAs heterostructural material grown by molecular beam epitaxy (MBE). The sheet carrier density of the two-dimensional electron gas (2-DEG) measured at 77 K was linearly proportional to the number of high mobility electron channels, and reached 5.3 × 10¹²cm^-2for six-channel HEMT structures. Depletion-mode devices of the double-heterojunction HEMT were operated between negative pinchoff voltage and forward-biased gate voltage without any transconductance degradation. A peak extrinsic transconductance of 360 mS/mm at 300 K and 550 mS/mm at 77 K has been measured for a 1-µm gate-length double-heterojunction enhancement-mode device. An extremely high drain current of 800 mA/mm with a gate-to-drain avalanche breakdown voltage of 9 V was measured on six-channel devices.     

Ga2O3(Gd2O3)/InGaAsenhancement-mode n-channel MOSFETs

We have demonstrated the first Ga₂O₃(Gd₂O₃) insulated gate n-channel enhancement-mode In_0.53Ga_0.47As MOSFET's on InP semi-insulating substrate. Ga₂O₃(Gd₂ O₃) was electron beam deposited from a high purity single crystal Ga₅Gd₃O₁₂ source. The source and drain regions of the device were selectively implanted with Si to produce low resistance ohmic contacts. A 0.75-μm gate length device exhibits an extrinsic transconductance of 190 mS/mm, which is an order of magnitude improvement over previously reported enhancement-mode InGaAs MISFETs. The current gain cutoff frequency, f_t, and the maximum frequency of oscillation, f_max, of 7 and 10 GHz were obtained, respectively, for a 0.75×100 μm² gate dimension device at a gate voltage of 3 V and drain voltage of 2 V     

Enhancement-Mode GaAs MOSFETs With an In0.3 Ga0.7As Channel, a Mobility of Over 5000 cm2/V ·s, and Transconductance of Over 475 μS/μm

We present metal-gate high-k-dielectric enhancement-mode (e-mode) III-V MOSFETs with the highest reported effective mobility and transconductance to date. The devices employ a GaGdO high-k (k = 20) gate stack, a Pt gate, and a delta-doped InGaAs/AlGaAs/GaAs hetero-structure. Typical 1-mum gate length device figures of merit are given as follows: saturation drive current, I_d,sat = 407 muA/mum; threshold voltage, V_t = +0.26 V; maximum extrinsic transconductance, g_m = 477 muS/mum (the highest reported to date for a III-V MOSFET); gate leakage current, I_g = 30 pA; subthreshold swing, S = 102 mV/dec; on resistance, R_on = 1920 Omega-mum; I_on/I_off ratio = 6.3 x 10⁴; and output conductance, g_d = 11 mS/mm. A peak electron mobility of 5230 cm²/V. s was extracted from low-drain-bias measurements of 20 mum long-channel devices, which, to the authors' best knowledge, is the highest mobility extracted from any e-mode MOSFET. These transport and device data are highly encouraging for future high-performance n-channel complementary metal-oxide-semiconductor solutions based on III-V MOSFETs.     

Quantum-well p-channel AlGaAs/InGaAs/GaAs heterostructureinsulated-gate field-effect transistors with very high transconductance

Quantum-well p-channel pseudomorphic AlGaAs/InGaAs/GaAs heterostructure insulated-gate field-effect transistors with enhanced hole mobility are described. The devices exhibit room-temperature transconductance, transconductance parameter, and maximum drain current as high as 113 mS/mm, 305 mS/V/mm, and 94 mA/mm, respectively, in 0.8-μm-gate devices. Transconductance, transconductance parameter, and maximum drain current as high as 175 mS/mm, 800 mS/V/mm, and 180 mA/mm, respectively were obtained in 1-μm p-channel devices at 77 K. From the device data hole field-effect mobilities of 860 cm²/V-s at 300 K and 2815 cm²/V-s at 77 K have been deduced. The gate current causes the transconductance to drop (and even to change sign) at large voltage swings. Further improvement of the device characteristics may be obtained by minimizing the gate current. To this end, a type of device structure called the dipole heterostructure insulated-gate field-effect transistor is proposed     

A high-performance enhancement-mode AlGaN/GaN HEMT

An enhancement-mode AlGaN/GaN HEMT with a threshold voltage of 0.35 V was fabricated by fluorine plasma treatment.The enhancement-mode device demonstrates high-performance DC characteristics with a saturation current density of 667 mA/mm at a gate bias of 4 V and a peak transconductance of 201 mS/mm at a gate bias of 0.8 V.The current-gain cut-off frequency and the maximum oscillation frequency of the enhancement-mode device with a gate length of μm are 10.3 GHz and 12.5 GHz,respectively,which is comparable with the depletion-mode device.A numerical simulation supported by SIMS results was employed to give a reasonable explanation that the fluorine ions act as an acceptor trap center in the barrier layer.     

Model and analysis of a delta-doping field-effect transistors utilizing an InGaP/GaAs camel-gate structure

In this paper, the performances of a new δ-doping field-effect transistor utilizing an InGaP/GaAs camel-gate structure by theoretical and experimental analysis will be reported. An analytical model related to drain saturation current, transconductance, potential barrier height, gate-to-source depletion capacitance, and unit current gain frequency is developed to explain the device performances. The employments of n⁺-GaAs/p⁺-InGaP/n-GaAs heterostructure gate and the δ-doping channel with heavy-doping level were used to improve transconductance linearity and enhance current drivability. For a 1×100 μm² device, the experimental results show that a drain saturation current of 1120 mA/mm, a maximum transconductance of 240 mS/mm, and a large V_gs swing larger than 3.5 V with the transconductance higher than 200 mS/mm are obtained. In addition, the measured unit current gain frequency f_t is 22 GHz. These experimental results are consistent with theoretical analysis.     

AlSb/InAs HEMT's for low-voltage, high-speed applications

The design, fabrication, and characterization of 0.1 μm AlSb/InAs HEMT's are reported. These devices have an In_0.4Al _0.6As/AlSb composite barrier above the InAs channel and a p ⁺ GaSb layer within the AlSb buffer layer. The HEMT's exhibit a transconductance of 600 mS/mm and an f_T of 120 GHz at V_Ds=0.6 V. An intrinsic f_T of 160 GHz is obtained after the gate bonding pad capacitance is removed from an equivalent circuit. The present HEMT's have a noise figure of 1 dB with 14 dB associated gain at 4 GHz and V_Ds=0.4 V. Noise equivalent circuit simulation indicates that this noise figure is primarily limited by gate leakage current and that a noise figure of 0.3 dB at 4 GHz is achievable with expected technological improvements. HEMT's with a 0.5 μm gate length on the same wafer exhibit a transconductance of 1 S/mm and an intrinsic f_TL_g, product of 50 GHz-μm     

Anisotype, enhancement-mode, heterojunction gate field-effect transistors

Anisotype, p/sup +/-GaAs/n-In/sub 0.15/Ga/sub 0.85/As heterojunction field-effect transistors, grown by molecular beam epitaxy and fabricated by a self-aligned process, have been investigated for digital logic applications. Peak transconductance of 411 mS/mm and a K-value of 292 mA/V/sup 2//mm were obtained for an enhancement-mode device with gate length of 1 mu m. Preliminary analysis of a nonisolated device leads to a cut off frequency of 17.5 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     

4H-SiC MESFET with 2.8 W/mm power density at 1.8 GHz

MESFET's were fabricated using 4H-SiC substrates and epitaxy. The D.C., S-parameter, and output power characteristics of the 0.7 μm gate length, 332 μm gate width MESFET's were measured. At ν_ds =25 V the current density was about 300 mA/mm and the maximum transconductance was in the range of 38-42 mS/mm. The device had 9.3 dB gain at 5 GHz and f_max=12.9 GHz. At V_ds=54 V the power density was 2.8 W/mm with a power added efficiency=12.7%     

On the Pseudomorphic High Electron Mobility Transistors (PHEMTs) With a Low-Temperature Gate Approach

The characteristics of AlGaAs/InGaAs/GaAs depletion-mode (D-mode) and enhancement-mode (E-mode) pseudomorphic high electron mobility transistors (PHEMTs) fabricated using an electroless-plated (EP) deposition approach are investigated. Under the low-temperature and low-energy conditions, the EP deposition approach can form a better metal–semiconductor interface. For the studied devices, with a $hbox{1} times hbox{100} muhbox{m}^{2}$ gate dimension, excellent characteristics of the maximum drain saturation current (168.9 mA/mm) and extrinsic transconductance (225.8 mS/mm) are obtained for the D-mode device. The corresponding values for the E-mode device are 152.5 mA/mm and 211.7 mS/mm, respectively. Moreover, the EP approach also has the advantages of easy operation and low cost.      

High-performance InGaP/InxGa1-xAs HEMT withan inverted delta-doped V-shaped channel structure

This letter reports a new and high-performance InGaP/In_xGa_1-xAs high electron mobility transistor (HEMT) with an inverted delta-doped V-shaped channel. Due to the presence of V-shaped inverted delta-doped InGaP/In_xGa_1-x As structure, good carrier confinement and a flat and wide transconductance operation regime are expected. Experimentally, the fabricated device (1×100 μm²) shows a high gate-to-drain breakdown voltage of 30 V and a high output drain saturation current density of 826 mA/mm at V_GS=2.5 V. The high transconductance expands over a very broad operation range with the maximum value of 201 mS/mm at 300 K. Meanwhile, the studied device exhibits a good microwave frequency linearity     

Enhancement-mode quantum-well GexSi1-x PMOS

The authors demonstrate the feasibility of a p-channel quantum-well MOSFET on a Ge_xSi_1-x/Si heterostructure. The advantages of the enhancement-mode p-channel MOSFET device compared to GeSi MODFETs are its high impedance, channel mobility, and channel transconductance. The device shows good saturation and cutoff behaviour. A saturation transconductance of 64 mS/mm was measured for a 0.7-μm channel device at a drain-to-source voltage of -2.5 V. The channel mobility was found to be higher than that of a similarly processed Si p-channel MOSFET     

InAlAs/InGaAs metamorphic HEMT with high current density and highbreakdown voltage

An In_0.3Al_0.7As/In_0.3Ga_0.7 As metamorphic power high electron mobility transistor (HEMT) grown on GaAs has been developed. This structure with 30% indium content presents several advantages over P-HEMT on GaAs and LM-HEMT on InP. A 0.15-μm gate length device with a single δ doping exhibits a state-of-the-art current gain cut-off frequency F_t value of 125 GHz at V_ds=1.5 V, an extrinsic transconductance of 650 mS/mm and a current density of 750 mA/mm associated to a high breakdown voltage of -13 V, power measurements performed at 60 GHz demonstrate a maximum output power of 240 mW/mm with 6.4-dB power gain and a power added efficiency (PAE) of 25%. These are the first power results ever reported for any metamorphic HEMT     

High-speed enhancement-mode InP MISFET's grown by chloridevapor-phase epitaxy

The properties of enhancement-mode InP metal-insulator-semiconductor field-effect transistors fabricated on semi-insulating InP substrates are reported. The epitaxial layers of the device structure have been grown by chloride vapor-phase epitaxy. Short-circuit current gain cutoff frequencies of 29.6 GHz were measured for 1-μm-gate-length devices. For devices with submicrometer gate lengths, extrinsic transconductance values up to 300 mS/mm and short-circuit current-gain cutoff frequencies of 38.1 GHz were measured. SiO₂ deposited by electron beam evaporation and plasma-enhanced CVD Si₃N₄ have been utilized as gate insulators, and a drain current drift of 30% within the first 50 h of operation has been observed. The high-speed performance of these devices represent to the authors' knowledge the fastest InP-based MIS field-effect transistor demonstrated     

An InP MISFET with a power density of 1.8 W/mm at 30 GHz

The millimeter-wave power performance of a 75-μm×0.3-μm InP MISFET with SiO₂ insulator is presented. The combination of high intrinsic transconductance (120 mS/mm), current density (1 A/mm), and gate-source and gate-drain breakdown voltages (35 V) led to a record power density of 1.8 W/mm and 20% power-added efficiency at 30 GHz. This power density is the highest ever reported for any three-terminal device at this frequency