Millimeter-wave low-noise and high-power metamorphic HEMTamplifiers and devices on GaAs substrates

This paper reports on state of-the-art HEMT devices and circuit results utilizing 32% and 60% indium content InGaAs channel metamorphic technology on GaAs substrates. The 60% In metamorphic HEMT (MHEMT) has achieved an excellent 0.61-dB minimum noise figure with 11.8 dB of associated gain at 26 GHz. Using this MHEMT technology, two and three-stage Ka-band low-noise amplifiers (LNAs) have demonstrated <1.4-dB noise figure with 16 dB of gain and <1.7 with 26 dB of gain, respectively. The 32% In MHEMT device has overcome the <3.5-V drain bias limitation of other MHEMT power devices, showing a power density of 650 mW/mm at 35 GHz, with V_ds=6 V     

60-GHz high power performance In/sub 0.35/Al/sub 0.65/As-In/sub 0-35/Ga/sub 0.65/As metamorphic HEMTs on GaAs

We report on a double-pulse doped, double recess In/sub 0.35/Al/sub 0.65/As-In/sub 0.35/Ga/sub 0.65/As metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. This 0.15-/spl mu/m gate MHEMT exhibits excellent de characteristics, high current density of 750 mA/mm, extrinsic transconductance of 700 mS/mm. The on and off state breakdown are respectively of 5 and 13 V and defined It gate current density of 1 mA/mm. Power measurements at 60 GHz were performed on these devices. Biased between 2 and 5 V, they demonstrated a maximum output power of 390 mW/mm at 3.1 V of drain voltage with 2.8 dB power gain and a power added efficiency (PAE) of 18%. The output power at 1 dB gain compression is still of 300 mW/mm. Moreover, the linear power gain is of 5.2 dB. This is to our knowledge the best output power density of any MHEMT reported at this frequency.     

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%     

Extremely high transconductance Ge/Si0.4Ge0.6p-MODFET's grown by UHV-CVD

Ge-channel modulation-doped field-effect transistors (MODFET's) with extremely high transconductance are reported. The devices were fabricated on a compressive-strained Ge/Si_0.4Ge_0.6 heterostructure with a Hall mobility of 1750 cm²/Vs (30,900 cm²/Vs) at room temperature (77 K). Self-aligned, T-gate p-MODFET's with L_g=0.1 μm displayed an average peak extrinsic transconductance (g(m_ext)) of 439 mS/mm, at a drain-to-source bias voltage (V_ds) of -0.6 V, with the best device having a value of g(m_ext)=488 mS/mm. At 77 K, values as high as g(m_ext)=687 mS/mm were obtained at a bias voltage of only V_ds=-0.2 V. These devices also displayed a unity current gain cutoff frequency (f_T) of 42 GHz and maximum frequency of oscillation (f_max) of 86 GHz at V_ds=-0.6 V and -1.0 V, respectively     

DC and RF Characteristics of 0.15 pm Power Metamorphic HEMTs

DC and RF characteristics of 0.15 °m GaAs power metamorphic high electron mobility transistors (MHEMT) have been investigated. The 0.15 °m ° 100 °m MHEMT device shows a drain saturation current of 480 mA/mm, an extrinsic transconductance of 830 mS/mm, and a threshold voltage of ‐0.65 V. Uniformities of the threshold voltage and the maximum extrinsic transconductance across a 4‐inch wafer were 8.3% and 5.1%, respectively. The obtained cut‐off frequency and maximum frequency of oscillation are 141 GHz and 243 GHz, respectively. The 8 ° 50 °m MHEMT device shows 33.2% power‐added efficiency, an 18.1 dB power gain, and a 28.2 mW output power. A very low minimum noise figure of 0.79 dB and an associated gain of 10.56 dB at 26 GHz are obtained for the power MHEMT with an indium content of 53% in the InGaAs channel. This excellent noise characteristic is attributed to the drastic reduction of gate resistance by the T‐shaped gate with a wide head and improved device performance. This power MHEMT technology can be used toward 77 GHz band applications.     

DC and microwave performance of a 0.1 μm gate InAs/In0.52Al0.8As MODFET

The authors have measured and analyzed the performance characteristics of 0.1-μm gate InAs/In_0.52Al_0.48 MODFETs grown by molecular beam epitaxy. The transistors are characterized by measured g_m(max)=840 mS/mm, f_T=128 GHz, and a very high current carrying capability, e.g. I_dss=934 mA/mm at V _gs=0.4 V and V_ds=2.7 V. The value of f _T is estimated from extrapolation of the current gain (H ₂₁) at a -6 dB/octave rolloff. This is the first report on the microwave characteristics of an InAs-channel MODFET and establishes the superiority of this heterostructure system     

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     

Enhancement-mode Al0.66In0.34As/Ga0.67In0.33As metamorphic HEMT, modeling and measurements

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al_0.66In_0.34As/Ga_0.67In_0.33 As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 μm ×3 mm devices exhibited 30 mW/mm at 850 MHz     

DC and RF performance of LP-MOCVD grownAl0.25Ga0.75As/InxGa1-xAs(x=0.15-0.28) P-HEMT's with Si-delta doped GaAs layer

Si-delta-doped Al_0.25Ga_0.75As/In_xGa_1-xAs (x=0.15-0.28) P-HEMT's, prepared by LP-MOCVD, are investigated. The large conduction band discontinuity leads to 2-DEG density as high as 2.1×10¹²/cm² with an electron mobility of 7300 cm²/V·s at 300 K. The P-HEMT's with 0.7×60 μm gate have a maximum extrinsic transconductance of 380 mS/mm, and a maximum current density of 300 mA/mm. The S-parameter measurements indicate that the current gain and power gain cutoff frequencies are 30 and 61 GHz, respectively, The RF noise characteristics exhibit a minimum noise figure of 1.2 dB with an associated gain of 10 dB at 10 GHz. Due to the efficient doping technique, the electron mobility and transconductance obtained are among the best reported for MOCVD grown P-HEMT's with the similar structure     

Doubly strainedIn0.41Al0.59As/n+-In0.65Ga0.35As HFET with high breakdown voltage

An In_0.41Al_0.59As/n⁺-In_0.65 Ga_0.35As HFET on InP was designed and fabricated, using the following methodology to enhance device breakdown: a quantum-well channel to introduce electron quantization and increase the effective channel bandgap, a strained In_0.41Al_0.59As insulator, and the elimination of parasitic mesa-sidewall gate leakage. The In_0.65Ga_0.35As channel is optimally doped to N_D=6×10¹⁸ cm^-3. The resulting device (L_g=1.9 μm, W_g =200 μm) has f_t=14.9 GHz, f_max in the range of 85 to 101 GHz, MSG=17.6 dB at 12 GHz V_B=12.8 V, and I_D(max)=302 mA/mm. This structure offers the promise of high-voltage applications at high frequencies on InP     

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     

A high-power GaAs FET having buried plated heat sink forhigh-performance MMIC's

This paper reports an FET structure, named “Advanced SIV FET” (advanced source island via-hole FET). The developed structure contains a selectively formed buried PHS (plated heat sink) instead of having thick backside gold metal. In this FET, the thickness of the substrate under the active layer, which produces heat during operation, is set to be 30 μm with a buried 70 μm thick gold plated heat sink for achieving low thermal resistance, and the thickness of other portion of the chip is set to be 100 μm for low loss in microstrip lines and sufficient mechanical strength. This FET structure has provided higher power output and power added efficiency with great simplicity of wafer and chip handling. The experimental results have shown that an FET, of 1350 μm gate width, has achieved a superior low thermal resistance of 16°C/W corresponding to a maximum channel temperature of 42.1°C. RF performances, at V_ds=7 V, show a power output as high as 27.9 dBm with a power added efficiency of 32% at the 1 dB power compression point and a linear gain of 8.3 dB all at 18 GHz. It also has achieved an excellent power density of 0.54 W/mm at V_ds=8 V. This structure has shown mechanical reliability which conforms to MIL-STD-883     

0.3 dB minimum noise figure at 2.5 GHz of 0.13 μm Si/Si0.58Ge0.42 n-MODFETs

RF and microwave noise performances of strained Si/Si_0.58 Ge_0.42 n-MODFETs are presented for the first time. The 0.13 μm gate devices have de-embedded f_T=49 GHz, f_max =70 GHz and a record intrinsic g_m=700 mS/mm. A de-embedded minimum noise figure NF_min=0.3 dB with a 41 Ω noise resistance R_n and a 19 dB associated gain G_ass are obtained at 2.5 GHz, while NF_min=2.0 dB with G_ass=10 dB at 18 GHz. The noise parameters measured up to 18 GHz and from 10 to 180 mA/mm with high gain and low power dissipation show the potential of SiGe MODFETs for mobile communications     

InP-based HEMT's with Al0.48In0.52AsxP1-x Schottky layers

In this letter we report on the DC and RF performance of InP-based HEMT's with Al_0.48In_0.52As_xP_1-x Schottky layers and GaInAs/InP composite channels. By replacing the Al_0.48In_0.52As Schottky layer with Al_0.48 In_0.52As_xP_1-x we have been able to increase the bandgap of the Schottky layer and achieve record breakdown voltages for 0.15 μm gate-length InP-based HEMT's. The 0.15 μm gate-length HEMT's have gate-to-drain breakdown voltages of over 13 V with current densities of 620 mA/mm and maximum transconductances of 730 mS/mm. On a wafer with a higher sheet charge we have obtained gate-to-drain breakdown voltages of 10.5 V with current densities of over 900 mA/mm. These are the highest breakdown voltages reported for 0.15 μm gate-length InP-based HEMT's with such high current densities. At 10 GHz a 450 μm wide HEMT has demonstrated 350 mW (780 mW/mm) of output power with power-added efficiency of 60% and 12 dB gain     

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     

OMCVD-grown In0.4Al0.6As/InP quantum-wellHEMT

The transport properties and device characteristics of pseudomorphic In_0.4Al_0.6As/InP modulation-doped heterostructures are investigated. The existence of a two-dimensional electron gas at the heterojunction was confirmed by Shubnikov-de Haas measurements. A high electron mobility transistor (HEMT) having a gate length of 1.5 μm showed extrinsic transconductances and drain current densities as high as 160 mS/mm and 300 mA/mm, respectively. The HEMT also showed a very small output conductance of less than 2 mS/mm and high gate-drain breakdown voltage of larger than 15 V. These results show the great potential of this HEMT for high-voltage gain and high-power microwave applications     

Electron transport in 0.15-μm gate In0.52Al0.48As/In0.53Ga0.47As HEMT

Magneto-transport and cyclotron resonance measurements were made to determine directly the density, mobility, and the effective mass of the charge carriers in a high-performance 0.15-μm gate In_0.52 Al_0.48As/In_0.53Ga_0.47As high-electron-mobility transistor (HEMT) at low temperatures. At the gate voltage V_G=0 V, the carrier density n _g under the gate is 9×10¹¹ cm^-2, while outside of the gate region n_g=2.1×10¹² cm^-2. The mobility under the gate at 4.2 K is as low as 400 cm²/V-s when V_G<0.1 V and rapidly approaches 11000 cm²/V-s when V_G>0.1 V. The existence of this high mobility threshold is crucial to the operation of the device and sets its high-performance region in V_G>0.1 V     

Optimal pump wavelength in the4I15/2-4I13/2 absorption band for efficient Er3+-doped fiberamplifiers

The authors report the measured gain of a highly efficient erbium-doped fiber amplifier pumped at wavelengths between 1.46 and 1.51 μm. The optimal pump wavelength, λ_opt, was determined to be 1.475 μm. At this wavelength, the maximum gain coefficients for signals at 1.531 and 1.544 μm were 2.3 and 2.6 dB/mW, respectively. At λ_opt, high gains ranging from 32 dB at pump power P_p=20 mW up to 40 dB at P _p=80 mW were obtained. These modest pump powers are within the capabilities of currently available 1.48-μm diode lasers. The width about λ_opt for 3-dB gain variation exceeded 27 nm for P_p=10 mW and 40 nm for P_p >20 mW. With this weak dependence on pump wavelength, single-longitudinal-mode lasers do not have a significant advantage over practical Fabry-Perot multimode pump lasers     

Double-dopedIn0.35Al0.65As/In0.35Ga0.65As power heterojunction FET on GaAs substrate with 1 W outputpower

A double-doped metamorphic In_0.35Al_0.65As/In _0.35Ga_0.65As power heterojunction FET (HJFET) on GaAs substrate is demonstrated. The HJFET exhibits good dc characteristics, with gate forward turn on voltage of 1.0 V, breakdown voltage of 20 V, and maximum drain current of 490 mA/mm. Under RF operation at a frequency of 950 MHz, a power added efficiency of 63% with associated output power of 31.7 dBm is obtained at a gate width of 12.8 mm. This large gate width and state-of-the-art power performance in metamorphic HJFETS were enabled by a selective etching, sputtered WSi gate process and low surface roughness due to an Al_0.60Ga_0.40As_0.69Sb_0.31 strain relief buffer     

Enhancement-mode power heterojunction FET utilizingAl0.5Ga0.5As barrier layer with negligibleoperation gate current for digital cellular phones

We have developed a novel enhancement-mode double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET (HJFET) with a 5 nm thick Al_0.5Ga_0.5As barrier layer inserted between an In _0.2Ga_0.8As channel layer and an upper Al_0.2 Ga_0.8As electron supply layer. The Al_0.5Ga _0.5As barrier layer reduces gate current under high forward gate bias voltage, resulting in a high forward gate turn-on voltage (V _F) of 0.87 V, which is 170 mV higher than that of an HJFET without the barrier layer. Suppression of gate current assisted by a parallel conduction path in the upper electron supply layer was found to be also important for achieving the high V_F. The developed device exhibited a high maximum drain current of 300 mA/mm with a threshold voltage of 0.17 V. A 950 MHz PDC power performance was evaluated under single 3.5 V operation. An HJFET with a 0.5 μm long gate exhibited 0.92 W output power and 63.6% power-added efficiency with 0.08 mA gate current (I_g) at -48 dBc adjacent channel leakage power at 50 kHz off-center frequency. This I_g is one-thirteenth to that of the HJFET without the barrier layer. These results indicate that the developed enhancement-mode HJFET is suitable for single low voltage operation power applications