Fabrication of depletion-mode GaAs MOSFET with a selectiveoxidation process by using metal as the mask

The n-channel depletion-mode GaAs MOSFETs with a selective liquid phase chemical-enhanced oxidation method at low temperature by using metal as the mask (M-SLPCEO) are demonstrated. The proposed process can simplify one mask to fabricate GaAs MOSFET and grow reliable gate oxide films as well as side-wall passivation layers at the same time. The 1 μm gate-length MOSFET with a gate oxide thickness of 35 nm shows a transconductance of 90 mS/mm and a maximum drain current density larger than 350 mA/mm. In addition, a short-circuit current gain cutoff frequency f_T of 6.5 GHz and a maximum oscillation frequency f _max of 18.3 GHz have been achieved from the 1 μm×100 μm GaAs MOSFET     

Demonstration of submicron depletion-mode GaAs MOSFETs withnegligible drain current drift and hysteresis

We successfully fabricated submicron depletion-mode GaAs MOSFETs with negligible hysteresis and drift in drain current using Ga₂ O₃(Gd₂O₃) as the gate oxide. The 0.8-μm gate-length device shows a maximum drain current density of 450 mA/mm and a peak extrinsic transconductance of 130 mS/mm. A short-circuit current gain cutoff frequency (f_T) of 17 GHz and a maximum oscillation frequency (f_max) of 60 GHz were obtained from the 0.8 μm×60 μm device. The absence of drain current drift and hysteresis along with excellent characteristics in the submicron devices is a significant advance toward the manufacture of commercially useful GaAs MOSFETs     

Noise performance of low power 0.25 micron gate ion implantedD-mode GaAs MESFET for wireless applications

We report on the noise performance of low power 0.25 μm gate ion implanted D-mode GaAs MESFETs suitable for wireless personal communication applications. The 0.25 μm×200 μm D-mode MESFET has a f_t of 18 GHz and f_max of 33 GHz at a power level of 1 mW (power density of 5 mW/mm). The noise characteristics at 4 GHz for the D-mode MESFET are F_min=0.65 dB and G_assoc =13 dB at 1 mW. These results demonstrate that the GaAs D-mode MESFET is also an excellent choice for low power personal communication applications     

High-linearity high-current-drivabilityGa0.51In0.49P/GaAs MISFET usingGa0.51In0.49P airbridge gate structure grown byGSMBE

A novel structure Ga_0.51In_0.49P/GaAs MISFET with an undoped Ga_0.51In_0.49P layer serving as the airbridge between active region and gate pad was first designed and fabricated. Wide and flat characteristics of g_m and f_max versus drain current or gate voltage were achieved. The device also showed a very high maximum current density (610 mA/mm) and a very high gate-to-drain breakdown voltage (25 V). Parasitic capacitances and leakage currents were minimized by the airbridge gate structure and thus high f_T of 22 GHz and high f_max of 40 GHz for 1 μm gate length devices were attained. To our knowledge, both were the best reported values for 1 μm gate GaAs channel FET's     

Direct ion-implanted 0.12 μm GaAs MESFET with ft of121 GHz and fmax of 160 GHz

An 0.12 μm gate length direct ion-implanted GaAs MESFET exhibiting excellent DC and microwave characteristics has been developed. By using a shallow implant schedule to form a highly-doped channel and an AsH₃ overpressure annealing system to optimize the shallow dopant profile, the GaAs MESFET performance was further improved. Peak transconductance of 500 mS/mm was obtained at I_ds =380 mA/mm. A noise figure of 0.9 dB with associated gain of 8.9 dB were achieved at 18 GHz. The current gain cutoff frequency f_max of 160 GHz indicates the suitability of this 0.12 μm T-gate device for millimeter-wave IC applications     

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     

High-frequency characterization of sub-0.25-μm fully depletedsilicon-on-insulator MOSFETs

A cutoff frequency, f_T, of 85 GHz was measured on a fully-depleted silicon-on-insulator (FDSOI) n-MOSFET with a gate length of 0.15 μm. The p-MOSFET with 0.22-μm gate length has an f_T of 42 GHz. The high-frequency equivalent circuits were derived from scattering parameters for MOSFETs with various gate lengths. The effects of gate length and other device parameters on the performance of FDSOI MOSFETs at RF are discussed     

High performance GaAs JFET with shallow implanted Cd-gate

Shallow p⁺-regions in GaAs, formed by Cd ion implantation, have been used as the gate region for GaAs JFETs. 0.7 μm gate length JFETs demonstrated a transconductance of 165 mS/mm a saturation current of 130 mA/mm, an f_t of 26 GHz, and an f _max of 42 GHz. These frequency metrics are superior to previous Zn-gate JFETs of similar dimensions     

Experimental high performance sub-0.1 μm channel nMOSFET's

Very high performance sub-0.1 μm channel nMOSFET's are fabricated with 35 Å gate oxide and shallow source-drain extensions. An 8.8-ps/stage delay at V_dd=1.5 V is recorded from a 0.08 μm channel nMOS ring oscillator at 85 K. The room temperature delay is 11.3 ps/stage. These are the fastest switching speeds reported to date for any silicon devices at these temperatures. Cutoff frequencies (f_T) of a 0.08 μm channel device are 93 GHz at 300 K, and 119 GHz at 85 K, respectively. Record saturation transconductances, 740 mS/mm at 300 K and 1040 mS/mm at 85 K, are obtained from a 0.05 μm channel device. Good subthreshold characteristics are achieved for 0.09 μm channel devices with a source-drain halo process     

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     

An all-implanted, self-aligned, GaAs JFET with a nonalloyedW/p+-GaAs ohmic gate contact

We describe a self-aligned, refractory metal gate contact, enhancement mode, GaAs junction field effect transistor (JFET) where all impurity doping was done by ion implantation. Processing conditions are presented for realizing a high gate turn-on voltage (~1.0 V at 1 mA/mm of gate current) relative to GaAs MESFET's. The high gate turn-on voltage is the result of optimizing the p⁺-gate implant and anneal to achieve a nonalloyed ohmic contact between the implanted p⁺-GaAs and the sputter deposited tungsten gate contact. Initial nominally 1.0 μm×50 μm n-JFET's have a transconductance of 85 mS/mm and f_t of 11.4 GHz     

A novel 0.1 μm MOSFET structure with inverted sidewall andrecessed channel

To solve the problems of trade-off between the short channel effect and the performance enhancement of sub-quartermicrometer MOSFETs, we have developed a recessed channel MOSFET structure called ISRC (Inverted-Sidewall Recessed-Channel). The oxide thickness is 4 nm and the effective channel length is 0.1 μm, which is the smallest Si-MOSFET ever reported in the recessed channel structures. The maximum saturation transconductance at V_D=2 V is 446 mS/mm for the 0.1 μm n-channel device. The threshold voltage roll-off is kept within 64 mV when the gate length varies from 1.4 μm to 0.1 μm and good subthreshold characteristics are achieved for 0.1 μm channel device     

Metamorphic In0.4Al0.6As/In0.4Ga0.6As HEMTs on GaAs substrate

New In_0.4Al_0.6As/In_0.4Ga_0.6 As metamorphic (MM) high electron mobility transistors (HEMTs) have been successfully fabricated on GaAs substrate with T-shaped gate lengths varying from 0.1 to 0.25 μm. The Schottky characteristics are a forward turn-on voltage of 0.7 V and a gate breakdown voltage of -10.5 V. These new MM-HEMTs exhibit typical drain currents of 600 mA/mm and extrinsic transconductance superior to 720 mS/mm. An extrinsic current cutoff frequency f_T of 195 GHz is achieved with the 0.1-μm gate length device. These results are the first reported for In_0.4 Al_0.6As/In_0.4Ga_0.6As MM-HEMTs on GaAs substrate     

Metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with a novelcomposite channels design

We report on fabrication and performance of novel 0.13 μm T-gate metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with composite InGaAs channels, combining the superior transport properties of In_0.52Ga_0.48As with low-impact ionization in the In_0.32Ga_0.68As subchannel. These devices exhibit excellent DC characteristics, high drain currents of 750 mA/mm, extrinsic transconductances of 600 mS/mm, combined with still very low output conductance values of 20 mS/mm, and high channel and gate breakdown voltages. The use of a composite InGaAs channels leads to excellent cut-off frequencies: f_max of 350 GHz and an f_T 160 GHz at V_DS=1.5 V. These are the best microwave frequency results ever reported for any FET on GaAs substrate     

DC and AC characteristics of delta-doped GaAs FET

Molecular-beam-epitaxy-grown GaAs field-effect transistors (FETs) using a delta-doped channel are discussed. FETs having gate lengths of 1.3 μm showed transconductances as high as 290 mS/mm at a current density of 200 mA/mm. The measured f_T was 14.5 GHz and the extracted f_max was 30 GHz. These results are the best reported in a FET with this material structure having a delta-doped channel     

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%     

3-mm double-heterojunction microwave power HEMT fabricated byselective RIE

Current-voltage and initial RF measurements are presented on a double-heterojunction HEMT (high-electron-mobility transistor) structure designed for power MMIC applications. The device structure is grown by molecular-beam epitaxy and uses a spatially variant superlattice to improve the performance of the inverted AlGaAs/GaAs interface. Gate recessing is achieved using a hybrid wet-chemical selective dry etching process. For selective dry etching, reactive ion etching with a >600:1 selectivity for GaAs over AlGaAs is used to control the recess depth. The room temperature DC characteristics for a 3-mm power FET (0.7- μm gate) display an I_dss of 370 mA/mm, a peak transconductance of 180 mS/mm, and a maximum gate-to-drain breakdown of 22 V. Large-signal microwave measurements at 5.5 GHz yielded a saturated output power of 1.3 W (31.2 dBm), 8.3-dB large-signal gain, and a peak power-added efficiency of 55%     

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     

Low noiseIn0.32(AlGa)0.68As/In0.43Ga0.57As metamorphic HEMT on GaAs substrate with 850 mW/mm output powerdensity

A double-pulse-doped InAlGaAs/In_0.43Ga_0.57As metamorphic high electron mobility transistor (MHEMT) on a GaAs substrate is demonstrated with state-of-the-art noise and power performance, This 0.15 μm T-gate MHEMT exhibits high on- and off-state breakdown (V_ds>6 V and V_dg>13 V, respectively) which allows biasing at V_ds>5 V. The 0.6 mm device shows >27 dBm output power (850 mW/mm) at 35 GHz-the highest reported power density of any MHEMT. Additionally, a smaller gate periphery 2×50 μm (0.1 mm) 43% MHEMT exhibits a F_min=1.18 dB and 10.7 dB associated gain at 25 GHz, and also is the first noise measurement of a -40% In MHEMT. A double recess process with selective etch chemistries provides for high yields     

Performance of interface engineeredSiNx/ICL/InP/In0.53Ga0.47As/InP dopedchannel HIGFET's

SiN_x/InP/InGaAs doped channel passivated heterojunction insulated gate field effect transistors (HIGFETs) have been fabricated for the first time using an improved In-S interface control layer (ICL). The insulated gate HIGFETs exhibit very low gate leakage (10 nA@V_GS =±5 V) and I_DS (sat) of 250 mA/mm. The doped channel improves the DC characteristics and the HIGFETs show transconductance of 140-150 mS/mm (L_g=2 μm), f_t of 5-6 GHz (L_g=3 μm), and power gain of 14.2 dB at 3 GHz. The ICL HIGFET technology is promising for high frequency applications