Enhanced microwave performance of ion-implanted MESFET with graded GaAs/AlGaAs heterojunctions

Ion-implanted MESFETs have been fabricated on an inverted GaAs/AlGaAs heterostructure. The aluminium concentration in the AlGaAs is graded from 0% at the substrate to 30% at the heterointerface. A maximum extrinsic transconductance of 410 mS/mm is achieved with 0.5 mu m gate devices. This heterojunction ion-implanted FET (HIFET) also exhibits enhanced microwave performance, especially at low drain current, when compared to conventional ion-implanted GaAs MESFETs. At 20% of I/sub dss/, the current gain cutoff frequency f/sub t/ is 40 GHz, which increases up to a maximum value of 47 GHz as the drain current rises. These characteristics of high f/sub t/ and high gain at low current are advantageous for low-noise applications.<>     

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     

GaAs MOSFET using InAlP native oxide as gate dielectric

GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using wet thermally oxidized InAlP as the gate insulator are reported for the first time. Leakage current measurements show that the 11-nm-thick native oxide grown from an In/sub 0.49/Al/sub 0.51/P layer lattice-matched to GaAs has good insulating properties, with a measured leakage current density of 1.39/spl times/10/sup -7/ mA//spl mu/m/sup 2/ at 1 V bias. GaAs MOSFETs with InAlP native gate oxide have been fabricated with gate lengths from 7 to 2 /spl mu/m. Devices with 2-/spl mu/m-long gates exhibit a peak extrinsic transconductance of 24.2 mS/mm, an intrinsic transconductance of 63.8 mS/mm, a threshold voltage of 0.15 V, and an off-state gate-drain breakdown voltage of 21.2 V. Numerical Poisson's equation solutions provide close agreement with the measured sheet resistance and threshold voltage.     

New field-effect transistor with quantum wire and modulation-dopedheterostructures

A new field-effect transistor, consisting of an AlGaAs/GaAs heterostructure and an (AlAs)_0.25(GaAs)_0.75 vertical superlattice, is fabricated. It has a large transconductance of 14 mS/mm at a gate length of 250 μm, corresponding to a transconductance of 3.5 S/mm for 1 μm gate length. Hall measurement revealed a novel FET operation mode called `velocity modulation'     

High DC and microwave characteristics of subhalf-micrometre gate ion-implanted GaAs MESFETs using trilayer deep UV lithography

Subhalf-micrometre gate length ion-implanted GaAs MESFETs have been fabricated on 3 inch diameter substrates using trilayer deep UV lithography. Implanted MESFETs with 0.3 mu m gate lengths exhibit a maximum extrinsic transconductance of 205 mS/mm at a drain current of 600 mA/mm. From S-parameter measurements, a current gain cutoff frequency f/sub t/ of 56 GHz and a maximum available gain cutoff frequency f/sub max/ greater than 90 GHz are achieved. The gate-to-drain diode characteristics of the devices show a sharp breakdown voltage of 13-15 V. The high drain current-drain voltage and microwave characteristics indicate that ion-implanted technology with trilayer deep UV lithography has potential for the manufacture of power devices and amplifiers for Q-band communication applications. This is the first reported result using trilayer deep UV lithography to demonstrate both f/sub t/ over 56 GHz and 13-15 V gate-to-drain breakdown on 0.3 mu m gate-length ion-implanted GaAs MESFETs.<>     

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     

Monolithic integration of Si MOSFET's and GaAs MESFET's

Integration of Si MOSFET's and GaAs MESFET's on a monolithic GaAs/Si (MGS) substrate has been demonstrated. The GaAs MESFET's have transconductance of 150 mS/mm for a gate length of 1 µm, and the Si MOSFET's have transconductance of 19 mS/mm for a gate length of 5 µm and an oxide thickness of 800 Å. These characteristics are comparable to those for devices fabricated on separate GaAs and Si substrates.     

High performance of induced-channel heterojunction field-effect transistor (HFET)

AlGaAs/GaAs high-performance, minority-carrier, induced-channel, heterojunction field-effect transistors (HFETs) fabricated on semi-insulating GaAs using molecular beam epitaxy (MBE) are reported. A 0.6 mu m self-aligned gate HFET exhibited a room-temperature transconductance of 540 mS/mm with a cutoff frequency of 25 GHz.<>     

High-performance 0.1-/spl mu/m In/sub 0.4/AlAs/In/sub 0.35/GaAs MHEMTs with Ar plasma treatment

High-performance 0.1-/spl mu/m In/sub 0.4/AlAs/In/sub 0.35/GaAs metamorphic high-electron mobility transistors (MHEMTs) on GaAs substrate have been successfully fabricated with Ar plasma treatment. Before the gate Schottky metallization, the devices were treated with Ar plasma, which might clean and improve the surface of exposed barrier layer. The devices fabricated with Ar plasma treatment exhibited the excellent characteristics such as 50% reduction of the reverse gate leakage currents, the improved Schottky ideality factor of 1.37, high extrinsic transconductance of 700 mS/mm, and high maximum drain current density of 780 mA/mm. And the cutoff frequency f/sub T/ as high as 210 GHz was achieved. To our knowledge, this is the best reported cutoff frequency for a 0.1-/spl mu/m MHEMT with an indium content of 35% in the channel.     

A 630-mS/mm GaAs MESFET with Au/WSiN refractory metal gate

GaAs MESFET's with a gate length as low as 0.2 μm have been successfully fabricated with Au/WSiN refractory metal gate n⁺-self-aligned ion-implantation technology. A very thin channel layer with high carrier concentration was realized with 10-keV ion implantation of Si and rapid thermal annealing. Low-energy implantation of the n⁺-contact regions was examined to reduce substrate leakage current. The 0.2-μm gate-length devices exhibited a maximum transconductance of 630 mS/mm and an intrinsic transconductance of 920 mS/mm at a threshold voltage of -0.14 V     

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.     

Electric parameter evolutions against gatelength and bias in ultrashort gate AlGaAs/GaAs HEMTs

The electric parameter evolutions of state of the art ultrashort gate planar doped AlGaAs/GaAs HEMTs are studied against gatelength l/sub g/=0.4-0.1 mu m and bias. The best value of maximum intrinsic transconductance obtained is g/sub m0max/=800 mS/mm at l/sub g/=0.15 mu m and the measured cutoff frequency is f/sub t/=125 GHz at l/sub g/=0.1 mu m.<>     

Ultra high transconductance 0.25 mu m gate MESFET with strained InGaAs buffer layer

The authors have successfully fabricated MBE-grown GaAs field effect transistors employing a strained MQW buffer layer. Quarter micron gate device showed transconductance as high as 1.460 mS/mm (900 mS/mm extrinsic) at a current density of 620 mA/mm. The measured f/sub c/ was 75 GHz. These high transconductances are, to the authors' knowledge, the best reported for GaAs MESFETs.<>     

High transconductance InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistors

Pseudomorphic In0.15Ga0.85As/Al0.15Ga0.85As modulation-doped field effect transistors (MODFET's) exhibiting extremely good dc characteristics have been successfully fabricated, dc transconductance in these strained-layer structures of 270 mS/mm were measured for 1-µm gate, normally-on devices at 300 K. Maximum drain current levels are 290 mA/mm, with excellent pinch-off and saturation characteristics. The transconductance increased to 360 mS/mm at 77 K while no persistent photoconductivity or drain collapse was observed. Preliminary microwave results indicate a 300-K current gain cutoff frequency of about 20 GHz. These results are equivalent to the best GaAs/AlGaAs MODFET results and are due in part to the improved transport properties and carrier confinement in the InGaAs quantum well.     

High-performance In0.08Ga0.92As MESFETs onGaAs(100) substrates

In_0.08Ga_0.92As MESFETs were grown in GaAs (100) substrates by molecular beam epitaxy (MBE). The structure comprised an undoped compositionally graded In_xGa_1-x As buffer layer, an In_0.08Ga_0.92As active layer, and an n⁺-In_0.08Ga_0.92As cap layer. FETs with 50-μm width and 0.4-μm gate length were fabricated using the standard processing technique. The best device showed a maximum current density of 700 mA/mm and a transconductance of 400 mS/mm. The transconductance is extremely high for the doping level used and is comparable to that of a 0.25-μm gate GaAs MESFET with an active layer doped to 10¹⁸ cm^-3. The current-gain cutoff frequency was 36 GHz and the power-gain cutoff frequency was 65 GHz. The current gain cutoff frequency is comparable to that of a 0.25-μm gate GaAs MESFET     

Depletion-mode GaAs SISFET's by selective ion implantation

Silicon donors have been implanted through the gate and into the (Al,Ga)As insulator of a GaAs SISFET structure in order to produce a negative shift in the device threshold voltage in selective areas of the wafer. The depletion-mode devices fabricated in this manner have controllable threshold voltage, high transconductance (350 mS/mm at 300 K and 380 mS/mm at 77 K for 1-µm gate-length devices), and low gate leakage characteristics. Such devices are suitable for enhance-deplete GaAs SISFET logic circuits.     

Reduced short-channel effects in submicron N-HIGFET technologyusing sidewalls

In this letter, 0.35 μm gate length pseudomorphic AlGaAs/InGaAs/GaAs heterostructure insulated-gate field-effect-transistors (HIGFETs) have been fabricated on GaAs. The short-channel effects have been reduced by using a sidewall technology. A high current density and a high transconductance were obtained, reflectively, 510 mA/mm and 550 mS/mm, in addition to a high value of extrinsic current gain cutoff frequency F_T=44 GHz. The dependencies of subthreshold current, threshold voltage, and output conductance on gate length have been emphasised     

High-efficiency GaAs power MESFETs prepared by ion implantation

GaAs power MESFETs have been fabricated using ion implantation to form channel layers. A 1 ?m gate length by 2400 ?m gate width device has demonstrated an output power of 1.63 W with 6.9 dB associated gain, 35% power-added efficiency and 9.7 dB linear gain at 10 GHz. The transconductance of this device is 280 mS, which corresponds to 117 mS/mm. This result demonstrates that excellent GaAs power MESFETs can be made by ion implantation, and is comparable to average results demonstrated by devices made by AsCl3 vapour phase epitaxy.     

Self-aligned GaAs gate heterojunction SISFET

A self-aligned GaAs gate heterojunction enhancement-mode SISFET with a layer structure of n+-GaAs/undoped Al0.5Ga0.5As/undoped GaAs is fabricated and shows a high transconductance and a low threshold voltage. The highest transconductance at both room temperature and at 77 K ever reported on a long-channel GaAs gate SISFET, 197 mS/mm and 313 mS/mm, respectively, is obtained.     

Self-aligned GaAs p-channel enhancement mode MOS heterostructurefield-effect transistor

Self-aligned GaAs enhancement mode MOS heterostructure field-effect transistors (MOS-HFET) have been successfully fabricated for the first time. The MOS devices employ a Ga₂O₃ gate oxide, an undoped Al_0.75Ga_0.25As spacer layer, and undoped In_0.2Ga_0.8As as channel layer. The p-channel devices with a gate length of 0.6 μm exhibit a maximum DC transconductance g_m of 51 mS/mm which is an improvement of more than two orders of magnitude over previously reported results. With the demonstration of a complete process flow and 66% of theoretical performance, GaAs MOS technology has moved into the realm of reality