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.<>     

High drain current-voltage product of submicrometer-gateion-implanted GaAs MESFET's for millimeter-wave operation

Ion-implanted GaAs MESFETs with gate lengths of 0.3 and 0.5 μm have been fabricated using optical lithography. The devices with 0.3- and 0.5-μm gate lengths exhibit extrinsic transconductances, at zero gate bias, of 200 and 180 mS/mm at drain currents of 400 and 420 mA/mm, respectively. The gate-to-drain diode characteristics of these two different gate-length devices show similar breakdown voltages of 13-15 V. From S-parameter measurements, current-gain cutoff frequencies, f _ts, of 56 and 30 GHz are obtained for 0.3- and 0.5-μm gate-length devices, respectively. The high drain current-voltage product and the microwave performance indicate that ion-implanted technology has the potential to be used to manufacture power devices for millimeter-wave applications     

High-performance millimeter-wave ion-implanted GaAs MESFETs

GaAs MESFETs (metal-epitaxial-semiconductor-field-effect transistors) with ion-implanted active channels have been fabricated on 3-in-diameter GaAs substrates which demonstrate device performance comparable with that of AlGaAs/InGaAs pseudomorphic HEMT (high-electron-mobility transistor) devices. Implanted MESFETs with 0.5-μm gate lengths exhibit an extrinsic transconductance of 350 mS/mm. From S-parameter measurements, a current-gain cutoff frequency f₁ of 48 GHz and a maximum-available-gain cutoff frequency f_max greater than 100 GHz are achieved. These results clearly demonstrate the suitability of ion-implanted MESFET technology for millimeter-wave discrete device, high-density digital, and monolithic microwave and millimeter-wave IC applications     

High-performance 0.1-μm gate enhancement-mode InAlAs/InGaAsHEMT's using two-step recessed gate technology

Novel approach for making high-performance enhancement-mode InAlAs/InGaAs HEMT's (E-HEMT's) is described for the first time. Most important issue for the fabrication of E-HEMT's is the suppression of the parasitic resistance due to side-etching around the gate periphery during gate recess etching. Two-step recessed gate technology is utilized for this purpose. The first step of the gate recess etching removes cap layers wet-chemically down to an InP recess-stopping layer and the second step removes only the recess-stopping layer by Ar plasma etching. The parasitic component for source resistance is successfully reduced to less than 0.35 Ω·mm. Etching selectivities for both steps are sufficient not to degrade uniformity of devices on the wafer. The resulting structure achieves a positive threshold voltage of 49.0 mV with high transconductance. Due to the etching selectivity, the standard deviation of the threshold voltage is as small as 13.3 mV on a 3-in wafer. A cutoff frequency of 208 GHz is obtained for the 0.1-μm gate E-HEMT's. This is therefore one of the promising devices for ultra-high-speed applications     

Super-low-noise performance of direct-ion-implanted 0.25-μm-gateGaAs MESFET's

The authors report on advanced ion implantation GaAs MESFET technology using a 0.25-μm `T' gate for super-low-noise microwave and millimeter-wave IC applications. The 0.25×200-μm-gate GaAs MESFETs achieved 0.56-dB noise figure with 13.1-dB associated gain at 50% I_DSS and 0.6 dB noise figure with 16.5-dB associated gain at 100% I_DSS at a measured frequency of 10 GHz. The measured noise figure is comparable to the best noise performance of AlGaAs/GaAs HEMTs and AlGaAs/InGaAs/GaAs pseudomorphic HEMTs     

Super low noise InGaP gated PHEMT

Very high performance InGaP/InGaAs/GaAs PHEMTs will be demonstrated. The fabricated InGaP gated PHEMTs devices with 0.25 × 160/cm² and 0.25 × 300 μm² of gate dimensions show 304 mA/mm and 330 mA/mm of saturation drain current at V_GS = 0 V, V_DS = 2 V, and 320 mS/mm and 302 mS/mm of extrinsic transconductances, respectively. Noise figures for 160 μm and 300 μm gate-width devices at 12 GHz are measured to be 0.46 dB with a 13 dB associated gain and 0.49 dB with a 12.85 dB associated gain, respectively. With such a high gain and low noise, the drain-to-gate breakdown voltage can be larger than 11 V. Standard deviation in the threshold voltage of 22 mV for 160 μm gate-width devices across a 4-in wafer can be achieved using a highly selective wet recess etching process. Good thermal stability of these InGaP gated PHEMTs is also presented     

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     

0.25-μm gate millimeter-wave ion-implanted GaAs MESFETs

Quarter-micrometer gated ion-implanted GaAs MESFETs which demonstrate device performance comparable to AlGaAs/InGaAs pseudomorphic HEMTs (high-electron mobility transistors) have been successfully fabricated on 3-in-diameter GaAs substrates. The MESFETs show a peak extrinsic transconductance of 480 mS/mm with a high channel current of 720 mA/mm. From S-parameter measurements, the MESFETs show a peak current-gain cutoff frequency f_t of 68 GHz with an average f_t of 62 GHz across the wafer. The 0.25-μm gate MESFETs also exhibit a maximum-available-gain cutoff frequency f_t greater than 100 GHz. These results are the first demonstration of potential volume production of high-performance ion-implanted MESFETs for millimeter-wave application     

Performance of GaAs MESFET's on InP substrates

The fabrication of GaAs MESFET's with 0.9-μm gate length on InP substrates, after growth of the heteroepitaxial material by metalorganic chemical vapor deposition (MOCVD) is described. The MESFETs exhibit extrinsic transconductances of 377 mS-mm^-1, the highest value yet reported for GaAs-on-InP devices. The drain I-V characteristic shows excellent saturation, a knee voltage of 0.75 V, and no light sensitivity. A unity current-gain cutoff frequency of 22 GHz and a maximum frequency of oscillation of 30 GHz are obtained for these MESFETs     

Ultrahigh-frequency performance of submicrometer-gate ion-implantedGaAs MESFETs

A study of the high-frequency performance of short-gate ion-implanted GaAs MESFETs with gate lengths of 0.3 and 0.5 μm is discussed. Excellent DC and microwave performance have been achieved with an emphasis on the reduction of effective gate length during device fabrication. From f_t of 83 and 48 GHz for 0.3-0.5-μm gate devices, respectively, an electron velocity of 1.5×10⁷ cm/s is estimated. An f_t of 240 GHz is also projected for a 0.1-μm-gate GaAs MESFET. These experimental results are believed to be comparable to those of the best HEMTs (high-electron-mobility transistors) reported and higher than those generally accepted for MESFETs     

Half-micrometer gate-length ion-implanted GaAs MESFET with 0.8-dBnoise figure at 16 GHz

Ion-implanted GaAs MESFETs with half-micrometer gate length have been fabricated on 3-in-diameter GaAs substrates. At 16 GHz, a minimum noise figure of 0.8 dB with an associated gain of 6.3 dB has been measured. This noise figure is believed to be the lowest ever reported for 0.5- and 0.25-μm ion-implanted MESFETs, and is comparable to that for 0.25-μm HEMTs at this frequency. By using the Fukui equation and the fitted equivalent circuit model, a K_f factor of 1.4 has been obtained. These results clearly demonstrate the potential of ion-implanted MESFET technology for K-band low-noise integrated circuit applications     

4H-SiC MESFET's with 42 GHz fmax

We report for the first time the development of state-of-the-art SiC MESFETs on high-resistivity 4H-SiC substrates. 0.5 μm gate MESFETs in this material show a new record high f_max of 42 GHz and RF gain of 5.1 dB at 20 GHz. These devices also show simultaneously high drain current, and gate-drain breakdown voltage of 500 mA/mm, and 100 V, respectively showing their potential for RF power applications     

A novel self-aligned gate process for half-micrometer gate GaAs ICsusing ECR-CVD

A substitutional self-aligned gate MESFET process for the half-micrometer gate GaAs IC that employs techniques of sidewall formation and precise pattern reversal using ECR (electron cyclotron resonance) CVD (chemical vapor deposition) is discussed. A FET with 0.45-μm gate length showed high performance characteristics, such as a maximum transconductance of 440 mS/mm and a cutoff frequency of 39 GHz. This process has two advantages over conventional substitutional and refractory gate processes. First, it can incorporate an LDD (lightly doped drain) structure. Second, since the photoresist dummy gates are precisely reversed without using reactive ion etching (RIE) at all, the gate length is dependent only on lithography. The process was demonstrated by the preliminary fabrication of a 16 b×16 b multiplier with 50% yield. The process, with high-performance device characteristics, should fine broad applications in both half-micrometer gate level LSIs and analog ICs     

InAlAs/InGaAs/InP MODFET's with uniform threshold voltage obtainedby selective wet gate recess

Excellent uniformity in the threshold voltage, transconductance, and current-gain cutoff frequency of InAlAs/InGaAs/InP MODFETs has been achieved using a selective wet gate recess process. An etch rate ratio of 25 was achieved for InGaAs over InAlAs using a 1:1 citric acid:H₂O₂ solution. By using this solution for gate recessing, the authors have achieved a threshold voltage standard deviation of 15 mV and a transconductance standard deviation of 15 mS/mm for devices across a quarter of a 2-in-diameter wafer. The average threshold voltage, transconductance, and current-gain cutoff frequency of 1.0-μm gate-length devices were -234 mV, 355 mS/mm, and 32 GHz, respectively     

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     

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     

High-performance double-recessed enhancement-mode metamorphic HEMTs on 4-in GaAs substrates

Enhancement-mode InAlAs/InGaAs/GaAs metamorphic HEMTs with a composite InGaAs channel and double-recessed 0.15-/spl mu/m gate length are presented. Epilayers with a room-temperature mobility of 10 000 cm/sup 2//V-s and a sheet charge of 3.5/spl times/10/sup 12/cm/sup -2/ are grown using molecular beam epitaxy on 4-in GaAs substrates. Fully selective double-recess and buried Pt-gate processes are employed to realize uniform and true enhancement-mode operation. Excellent dc and RF characteristics are achieved with threshold voltage, maximum drain current, extrinsic transconductance, and cutoff frequency of 0.3 V, 500 mA/mm, 850 mS/mm, and 128 GHz, respectively, as measured on 100-/spl mu/m gate width devices. The load pull measurements of 300-/spl mu/m gate width devices at 35 GHz yielded a 1-dB compression point output power density of 580 mW/mm, gain of 7.2 dB, and a power-added efficiency of 44% at 5 V of drain bias.     

⟨110⟩-oriented GaAs MESFETs

GaAs metal semiconductor field-effect transistors (MESFETs) have been successfully fabricated on molecular-beam epitaxial (MBE) films grown on the off-axis (110) GaAs substrate. The (110) substrates were tilted 6° toward the (111) Ga face in order to produce device quality two-dimensional MBE growth. Following the growth of a 0.4-μm undoped GaAs buffer, a 0.18-μm GaAs channel with a doping density of 3.4×10¹⁷ cm^-3 and a 0.12-μm contact layer with a doping density of 2×10¹⁸ cm^-3, both doped with Si, were grown. MESFET devices fabricated on this material show very low-gate leakage current, low output conductance, and an extrinsic transconductance of 200 mS/mm. A unity-current-gain cutoff frequency of 23 GHz and a maximum frequency of oscillation of 56 GHz have been achieved. These (110) GaAs MESFETs have demonstrated their potential for high-speed digital circuits as well as microwave power FET applications     

A Ku-band T-shaped gate GaAs power MESFET with high breakdownvoltage for satellite communications

^GaAs power MESFET's with 0.5-μm T-shaped gate for Ku-band power applications have been developed using a new self-aligned and optical lithography. It displays a maximum current density of 350 mA/mm, an uniform transconductance of 150 mS/mm and a high gate-to-drain breakdown voltage of 35 V. Both the high breakdown voltage and the uniform transconductance were achieved by the new MESFET design incorporating an undoped GaAs cap and a thick lightly doped active layers. The breakdown voltage is the highest one among the values reported on the power devices. The device exhibits 0.61 W/mm power density and 47% power added efficiency with 9.0 dB associated gain at a drain bias of 12 V and an operation frequency of 12 GHz     

Improvement in threshold-voltage uniformity in submicrometer GaAs MESFET's using an implanted p layer

A significant improvement in threshold-voltage uniformity for submicrometer gate GaAs MESFET's fabricated by direct Si implan, tation was observed using an optimized p-buried layer on conventional undoped LEC-grown substrates. Using an optimized Be-implantation scheme, we have achieved standard deviations of the threshold voltage as low as 7.6 mV from 13 × 13 FET arrays and only 16.8 mV across a 3-in wafer for FET's with a gate length of 0.6 µm. This is a very promising result for extending the GaAs MESFET IC technology into VLSI circuit complexity.