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     

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     

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     

Submicron-gate InP power MISFET's with improved output powerdensity at 18 and 20 GHz

The microwave characteristics at 18 and 20 GHz of submicron-gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFETs) for high output power density applications are presented. InP power MISFETs were fabricated with 0.7 μm gate lengths, 0.2 mm gate widths, and drain-source spacings of 2, 3 and 5 μm. The output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacings of 3 μm. At 18 GHz output power densities of 1.59 W/mm with a gain of 3.47 dB and a power-added efficiency of 20.0% were obtained for a drain-source spacing of 3 μm. At 20 GHz output power densities of 1.20 W/mm with a gain of 3.17 dB and a power-added efficiency of 13.6% were obtained for a drain-source spacing of 3 μm     

High-frequency performance of diamond field-effect transistor

The microwave performance of a diamond metal-semiconductor field-effect transistor (MESFET) is reported for the first time. MESFETs with a gate length of 2-3 μm and a source-gate spacing of 0.1 μm were fabricated on the hydrogen-terminated surface of an undoped diamond film grown by microwave plasma chemical vapor deposition (CVD) utilizing a self-aligned gate fabrication process. A maximum transconductance of 70 mS/mm was obtained on a 2 μm gate MESFET at V_GS=-1.5 V and V_DS=-5 V,for which a cutoff frequency f_T and a maximum oscillating frequency f_max of 2.2 GHz and 7 GHz were obtained, respectively     

A high performance super self-aligned 3 V/5 V BiCMOS technologywith extremely low parasitics for low-power mixed-signal applications

A high performance BiCMOS technology, BEST2 (Bipolar Enhanced super Self-aligned Technology) designed for supporting low-power multiGHz mixed-signal applications is presented. Process modules to produce low parasitic device structures are described. The developed BiCMOS process implemented with 1 μm design rules (0.5 μm as one nesting tolerance) has achieved f_l and f_max for npn bipolar (A_e=1×2 μm²) of 23 GHz and 24 GHz at V_ce=3 V, respectively, with BV_ceo⩾5.5 volts, and βV_A product of 2400. Typical measured ECL gate delay is 48 ps/37 ps per stage (A_e=1×2 μm² ; 500 mV swing) at 0.6 mA/2.1 mA switching currents, and CMOS gate delay (gate oxide=125 Å, L_eff=0.6 μm; V_th,nch =0.45 V; V_th,pch=-0.45 V) 70 ps/stage. A BiCMOS phase-locked-loop (emitter width=1 μm; gate L_eff=0.7 μm) has achieved 6 GHz operation at 2 V power supply with total power consumption of 60 mW     

Device characteristics of the GaN/InGaN-doped channel HFETs

First dc, small signal, and RF power characteristics of GaN/InGaN doped-channel heterojunction field effect transistors (HFETs) are reported. HFETs with a 1-μm gate length have demonstrated a maximum drain current of 272 mA/mm, a flat G_m around 65 mS/mm in a V _GS between -0.65 V and +2.0 V, and an on-state breakdown voltage over 50 V. Complete pinchoff was observed for a -3.5 V gate bias. Devices with a 1-μm gate length have exhibited an f_T of 8 GHz and f_max of 20 GHz. A saturated output power of 26 dBm was obtained at 1.9 GHz for a 1 μm×1 mm device     

High-breakdown-voltage Ga0.51In0.49P channelMESFET's grown by GSMBE

The first Ga_0.51In_0.49P channel MESFETs grown on a (100) GaAs substrate by GSMBE have been fabricated. A high gate-to-drain breakdown voltage of 42 V with a high maximum current density (320 mA/mm) was achieved. This result demonstrates that high-breakdown voltage could be attained by using Ga_0.51In _0.49P as the channel material. We also measured a high-maximum oscillation frequency (f_max) of 30 GHz for a 1.5 μm gate-length device. This value is quite high compared with other high-breakdown-voltage GaAs MESFET's or MISFET's with the same gate length     

Trapping effects and microwave power performance in AlGaN/GaN HEMTs

The dc small-signal, and microwave power output characteristics of AlGaN/GaN HEMTs are presented. A maximum drain current greater than 1 A/mm and a gate-drain breakdown voltage over 80 V have been attained. For a 0.4 μm gate length, an f_T of 30 GHz and an f_max of 70 GHz have been demonstrated. Trapping effects, attributed to surface and buffer layers, and their relationship to microwave power performance are discussed. It is demonstrated that gate lag is related to surface trapping and drain current collapse is associated with the properties of the GaN buffer layer. Through a reduction of these trapping effects, a CW power density of 3.3 W/mm and a pulsed power density of 6.7 W/mm have been achieved at 3.8 GHz     

High performance fully selective double recess InAlAs/InGaAs/InPHEMTs

InP HEMTs with a double recess 0.12 μm gate have been developed. The material structure was designed to be fully selective etched at both recess steps for improved uniformity and yield across the whole wafer. Devices demonstrated DC characteristics of extrinsic transconductances of 1000 mS/mm, maximum current density of 800 mA/mm and gate-drain reverse breakdown voltages of -7.8 V. Power measurements were performed at both 20 GHz and 60 GHz. At 20 GHz, the 6×75 μm devices yielded 65% maximum power added efficiency (PAE) with associated gain of 13.5 dB and output power of 185 mW/mm. When tuned for maximum output power it gave an output power density of 670 mW/mm with 15.6 dB gain and 49% PAE. At 60 GHz, maximum PAE of 30% has been measured with associated output power density of 290 mW/mm and gain of 7.4 dB. This represents the best power performance reported for InP-based double recess HEMT's     

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     

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     

High performance 0.1 μm gate-length p-type SiGe MODFET's andMOS-MODFET's

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide-semiconductor MODFET (MOS-MODFET) with 0.1 μm gate-length have been fabricated on a high hole mobility SiGe-Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g_m) of 142 mS/mm, a unity current gain cut-off frequency (f_T) of 45 GHz and a maximum oscillation frequency (f_MAX) of 81 GHz, 5 nm-thick high quality jet-vapor-deposited (JVD) SiO₂ was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA/μm at V_gs=6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g _m of 90 mS/mm, f_T of 38 GHz, and f_max of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF_min) of 1.29 dB and an associated power gain (G_a) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF _min of 0.92 dB and a G_a of 12 dB at 2 GHz. These DC, RF, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications     

Multigigahertz CMOS dual-modulus prescaler IC

A low-power CMOS dual-modulus (divide-by-128/129) prescaler IC is described. The IC has been fabricated with symmetric CMOS technology that optimizes simultaneously the characteristics of both the p-channel and n-channel transistors for low-power-supply-voltage operation. Two different gate oxide thicknesses of 175 and 100 Å have been used. The best prescalar fabricated with 175-Å gate oxide functions at 2.06 GHz with 25-m W power consumption (L_eff=0.5 μm; V_dd=3.5 V). Preliminary results for prescalars fabricated with 100-Å gate oxide show that 4.2-GHz operation is possible (L_eff=0.4 μm; V _dd=3.5 V). Power-supply voltage as low as 1.7 V can be used for the prescalar to function at 1 GHz with a power consumption of only 4 mW     

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     

The effect of surface passivation on the microwave characteristicsof undoped AlGaN/GaN HEMTs

Surface passivation of undoped AlGaN/CaN HEMT's reduces or eliminates the surface effects responsible for limiting both the RF current and breakdown voltages of the devices. Power measurements on a 2×125×0.5 μm AlGaN/GaN sapphire based HEMT demonstrate an increase in 4 GHz saturated output power from 1.0 W/mm [36% peak power-added efficiency (PAE)] to 2.0 W/mm (46% peak PAE) with 15 V applied to the drain in each case. Breakdown measurement data show a 25% average increase in breakdown voltage for 0.5 μm gate length HEMT's on the same wafer. Finally, 4 GHz power sweep data for a 2×75×0.4 μm AlGaN/GaN HEMT on sapphire processed using the Si₃N₄ passivation layer produced 4.0 W/mm saturated output power at 41% PAE (25 V drain bias). This result represents the highest reported microwave power density for undoped sapphire substrated AlGaN/GaN HEMT's     

InGaP/InGaAs Pseudomorphic Heterodoped-Channel FETs With a Field Plate and a Reduced Gate Length by Splitting Gate Metal

Depositing gate metal across a step undercut between the Schottky barrier layer and the insulator-like layer is employed to obtain a reduced gate length of 0.4 mum with an additional 0.6-mum field plate from a 1-mum gate window. Most dc and ac characteristics including current density (I_DSS=451mA/mm), transconductance (g_m,max=225mS/mm), breakdown voltages (V_BD(DS)/V _BD(GD)=22/-25.5V), gate-voltage swing (GVS=2.24V), cutoff, and maximum oscillation frequencies (f_t/f_max=17.2/32GHz) are improved as compared to those of a 1-mum gate device without field plate. At a V_DS of 4.0 V, a maximum power added efficiency of 36% with an output power of 13.9 dBm and a power gain of 8.7 dB are obtained at a frequency of 1.8 GHz. The saturated output power and the linear power gain are 316 mW/mm and 13 dB, respectively     

Measured microwave power performance of AlGaN/GaN MODFET

We report the first microwave power measurement on GaN FET's. At 2 GHz, a class A output power density of 1.1 W/mm with a power added efficiency of 18.6% was obtained on a 1 μm gate-length AlGaN/GaN MODFET. Mathematical simulation estimated that the transistor was operating at a channel temperature of 360°C as a result of the poor thermal conductivity of the sapphire substrate. Despite this serious heating problem, the power output density still rivals GaAs MESFET's     

0.3-μm gate length p-channel AlGaAs/InGaAs heterostructure fieldeffect transistors with high cut-off frequency

P-channel Heterostructure Field Effect Transistors (HFETs) with a 0.3-μm gate were fabricated by Mg ion implantation. The maximum transconductance was 68 mS/mm and there was no serious drain or gate leakage current, regardless of this short gate length. The gate turn on voltage (@I_gs=-1 μA/μm) was -2.1 V and its absolute value was large enough for use in complementary HFETs. S-parameters measurements showed a very high cut-off frequency of over 10 GHz. Results indicated the superiority of less-diffusive Mg ion implantation for forming p⁺-layer in p-channel HFETs     

Microwave operation of GaN/AlGaN-doped channel heterostructurefield effect transistors

We report on the microwave operation of 1 μm gate AlGaN/GaN doped channel heterostructure field effect transistors (DC-HFET's) with the cutoff frequency f_T of 18.3 GHz. These devices exhibit the cutoff frequency-gate length product in excess of 18 GHz·μm, comparable to that of the state-of-the-art GaAs MESFET's. We explain these improvements in the device performance by the increased sheet carrier density in the device channel and by a reduction in the parasitic series resistances, caused by doping the device channel