DC and RF characteristics of doped multichannelAlAs0.56Sb0.44/In0.53Ga0.47As field effect transistors with variable gate-lengths

Depletion-mode doped-channel field effect transistors (DCFETs) using a AlAs_0.56Sb_0.44/In_0.53Ga_0.47 As heterostructure with multiple channels grown by molecular beam epitaxy (MBE) on an InP substrate are presented. Devices with gate lengths ranging from 0.2 μm to 1.0 μm have been fabricated. Three doped In_0.53Ga_0.47As channels separated by undoped AlAs_0.56Sb_0.44 layers are used for the devices. The devices exhibit unity current gain cut-off frequencies typically between 18 GHz and 73 GHz and corresponding maximum oscillation frequencies typically between 60 GHz and 160 GHz. The multiple channel approach results in wide linearity of dc and RF performance of the device     

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     

Beat-frequency between measurements between C12O216and C12O218lasers

Several beat frequencies in the range below 6 GHz have been measured using a C¹²O2¹⁶laser and a C¹²O2¹⁸laser operating on several pairs of closely spaced lines in the 9.3-μm region.     

Al0.25In0.75P/Al0.48In0.52As/Ga0.35In 0.65As graded channelpseudomorphic HEMT's with high channel-breakdown voltage

A new Al_0.25In_0.75P/Al_0.48In_0.52 As/Ga_0.35In 0_.65As pseudomorphic HEMT where the InAs mole fraction of the Ga_1-xIn_xAs channel was graded (x=0.53→0.65→0.53) is described. The modification of the quantum well channel significantly improved breakdown characteristics. In addition, use of an Al_0.25In_0.75P Schottky layer increased the Schottky barrier height. Devices having 0.5 μm gate-length showed g_m of 520 mS/mm and I_max of 700 mA/mm. The gate-drain (BV_g-d) and source-drain (BV_d-s ) breakdown voltages were as high as -14 and 13 V, respectively. An f_T of 70 GHz and f_max of 90 GHz were obtained     

Characterization of surface-undoped In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobilitytransistors

High-performance 0.3-μm-gate-length surface-undoped In_0.52 Al_0.48As/In_0.53Ga_0.47As/InP high-electron-mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) have been characterized and compared with a surface-doped structure. At 18 GHz, the surface-undoped HEMT has achieved a maximum stable gain (MSG) of 19.2 dB compared to 16.0 dB for the surface-doped structure. The higher MSG value of the surface-undoped HEMTs is obtained due to the improved g_m/g₀ ratio associated with the surface-induced electric field spreading effect. Comparison of identical 0.3-×150-μm-gate devices fabricated on surface-undoped and -doped structures has shown greatly improved gate leakage characteristics and much lower output conductance for the surface-undoped structure. It is demonstrated that the surface potential, modulated by different surface layer designs, affects the charge control in the conducting channel, especially the carrier injection into the buffer, resulting in excess output conductance. Several millimeter-wave coplanar waveguide (CPW) monolithic distributed amplifiers have been successfully fabricated by using the surface-undoped HEMT structure. A high gain per stage distributed amplifier with 170-dB±1-dB small-signal gain across a frequency band of 24-40 GHz, a W-band monolithic integrated circuit with 6.4-dB gain at 94 GHz, and a broad bandwidth distributed amplifier with 5-dB gain across a frequency band of 5 to 100 GHz have been demonstrated by using the surface-undoped structures     

High-performance InP/In0.53Ga0.47As/InPdouble HBTs on GaAs substrates

InP/In_0.53Ga_0.47As/InP double heterojunction bipolar transistors (HBTs) were grown on GaAs substrates. A 140 GHz power-gain cutoff frequency f_max and a 207 GHz current-gain cutoff frequency f_τ were obtained, presently the highest reported values for metamorphic HBTs. The breakdown voltage BV_CEO was 5.5 V, while the dc current gain β was 76. High-thermal-conductivity InP metamorphic buffer layers were employed in order to minimize the device-thermal resistance     

MetamorphicIn0.53Ga0.47As/In0.52Al0.48As HEMTs on germanium substrates

We report for the first time the successful epitaxial growth and processing of high-performance metamorphic high electron mobility transistors (HEMTs) on Ge substrates, with a transconductance of 700 mS/mm and a saturation channel current of 650 mA/mm. To reduce parasitic capacitances due to the conductive substrate, a dry etch method based on CF₄ and O₂ reactive ion etching (RIE) is developed for selective substrate removal. Devices with 0.2 μm gate length display an increase of the extrinsic cut-off frequency f_T from 45 GHz before, to 75 GHz after substrate removal, whereas the maximum oscillation frequency f_max increases from 68 GHz to 95 GHz. Based on this excellent rf performance level, in combination with the highly selective thinning process, we think that Ge as a sacrificial substrate is a promising candidate for the integration of thinned individual HEMTs with passive circuitry on low-cost substrates. This could result in low-cost advanced hybrid systems for mass-market millimeter wave 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     

7.1 GHz bandwidth monolithically integratedIn0.53Ga0.47As/In0.52Al0.48As PIN-HBT transimpedance photoreceiver

A monolithically integrated photoreceiver using an InAlAs/InGaAs HBT-based transimpedance amplifier has been fabricated and characterized. The p-i-n photodiode is implemented using the base-collector junction of the HBT. The 5 μm×5 μm emitter area transistors have self-aligned base metal and non-alloyed Ti/Pt/Au contacts. Discrete transistors demonstrated f_T and f_max of 54 GHz and 51 GHz, respectively. The amplifier demonstrated a -3 dB transimpedance bandwidth of 10 GHz and a gain of 40 dBΩ. The integrated photoreceiver with a 10 μm×10 μm p-i-n photodiode showed a -3 dB bandwidth of 7.1 GHz     

Al0.3Ga0.7As/GaAs HEMT's under opticalillumination

Theoretical and experimental work for the DC and RF performance of depletion mode Al_0.3Ga_0.7As/GaAs HEMTs under optical illumination is presented. The photoconductive effect increasing the 2-DEG channel electron concentration and photovoltaic effect in the gate junction are considered. Optical tuning of a 2 GHz HEMT oscillator and optical control of the gain of a 2 to 6 GHz HEMT amplifier are presented and potential applications are described     

650-Å self-aligned-gate pseudomorphicAl0.48In0.52As/Ga0.2In0.8Ashigh electron mobility transistors

The authors report on the design and fabrication of a 650-Å self-aligned-gate pseudomorphic Al_0.48In_0.52As/Ga _0.2In_0.8As high electron mobility transistor (HEMT) with a state-of-the-art current gain cutoff frequency of over 300 GHz. This work clearly demonstrates the potential of sub-0.1-μm gate-length HEMTs for near-future microwave and millimeter-wave applications     

High-frequency submicrometerAl0.48In0.52As/In0.53Ga0.47As heterostructure bipolar transistors

The high speed scaling of an Al_0.48In_0.52As/In_0.53Ga_0.47 As submicrometer heterostructure bipolar transistor (HBT) is presented. Transistors with emitter dimensions of 0.5×11 and 3.5×3.5 μm² exhibit unity current-gain cutoff frequencies of 63 and 70 GHz, respectively. Emitter current density greater than 3.3×10⁵ A/cm² is demonstrated in a submicrometer AlInAs/InGaAs HBT. The analysis shows that the device speed is limited by the parasitic collector charging time     

Single- and double-heterojunction pseudomorphic In0.5(Al0.3Ga0.7)0.5P/In0.2Ga0.8As high electron mobility transistors grown by gas sourcemolecular beam epitaxy

In_0.5(Al_0.3Ga_0.7)_0.5 P/In_0.2Ga_0.8As single- and double-heterojunction pseudomorphic high electron mobility transistors (SH-PHEMTs and DH-PHEMTs) on GaAs grown by gas-source molecular beam epitaxy (GSMBE) were demonstrated for the first time. SH-PHEMTs with a 1-μm gate-length showed a peak extrinsic transconductance g_m of 293 mS/mm and a full channel current density I_max of 350 mA/mm. The corresponding values of g_m and I_max were 320 mS/mm and 550 mA/mm, respectively, for the DH-PHEMTs. A short-circuit current gain (H₂₁) cutoff frequency f_T of 21 GHz and a maximum oscillation frequency f_max of 64 GHz were obtained from a 1 μm DH device. The improved device performance is attributed to the large ΔE_c provided by the In_0.5(Al_0.3Ga_0.7)_0.5P/In _0.2Ga_0.8As heterojunctions. These results demonstrated that In_0.5(Al_0.3Ga_0.7)_0.5P/In _0.2Ga_0.8As PHEMT's are promising candidates for microwave power applications     

Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic doped-channel FET with high-current densityand high-breakdown voltage

Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs pseudomorphic doped-channel FETs exhibiting excellent DC and microwave characteristics were successfully fabricated. A high peak transconductance of 350 mS/mm, a high gate-drain breakdown voltage of 31 V and a high maximum current density (575 mA/mm) were achieved. These results demonstrate that high transconductance and high breakdown voltage could be attained by using In_0.15Ga_0.85As and Ga_0.51In_0.49P as the channel and insulator materials, respectively. We also measured a high-current gain cut-off frequency f_t of 23.3 GHz and a high maximum oscillation frequency f_max of 50.8 GHz for a 1-μm gate length device at 300 K. RF values where higher than those of other works of InGaAs channel pseudomorphic doped-channel FETs (DCFETs), high electron mobility transistors (HEMTs), and heterostructure FETs (HFETs) with the same gate length and were mainly attributed to higher transconductance due to higher mobility, while the DC values were comparable with the other works. The above results suggested that Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs doped channel FET's were were very suitable for microwave high power device application     

High performance 0.35 μm gate-length monolithicenhancement/depletion-mode metamorphicIn0.52Al0.48As/In0.53Ga0.47As HEMTs on GaAs substrates

Monolithic integration of enhancement (E)- and depletion (D)-mode metamorphic In_0.52Al_0.48As/In_0.53Ga_0.47 As/GaAs HEMTs with 0.35 μm gate-length is presented for the first time. Epilayers are grown on 3-inch SI GaAs substrates using molecular beam epitaxy. A mobility of 9550 cm²/V-s and a sheet density of 1.12×10^{12 -2} are achieved at room temperature. Buried Pt-gate was employed for E-mode devices to achieve a positive shift in the threshold voltage. Excellent characteristics are achieved with threshold voltage, maximum drain current, and extrinsic transconductance of 100 mV, 370 mA/mm and 660 mS/mm, respectively for E-mode devices, and -550 mV, 390 mA/mm and 510 mS/mm, respectively for D-mode devices. The unity current gain cutoff frequencies of 75 GHz for E-mode and 80 GHz for D-mode are reported     

Large enhancement of interband tunneling current densities of over105 A/cm2 inIn0.53Ga0.47As-based surface tunnel transistors

In_0.53Ga_0.47As-based Surface Tunnel Transistors (STT's), which control an interband tunneling current between an n-type channel and a p-type drain by an insulated gate, are investigated with the goal of increasing the tunneling current-density for high-speed operation. The fabricated devices enhanced an interband tunneling current density by a factor of 10² compared to the conventional GaAs-STT's due to a smaller bandgap energy and a lighter electron effective mass, and exhibited a clear gate-controlled negative differential resistance (NDR) characteristics with maximum tunneling current densities of over 10⁵ A/cm². The cutoff frequency (F_T) and maximum oscillation frequency (f_max ) of a fabricated device with a 1.0-μm gate length were estimated to be 7.9 GHz and 20 GHz, respectively, in the NDR region     

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     

An In0.52Al0.48As/n+-In0.53Ga0.47As MISFET with a heavily doped channel

An In0.52Al0.48As/n⁺-In0.53Ga0.47As MIS-type field-effect transistor (FET) with a channel doped at a 7 × 10¹⁷cm^-3level has been fabricated on an InP substrate. A device with a 2-µm channel length has yielded a maximum transconductance of 152 mS/mm,f_{T} = 12.4GHz, andf_{max} = 50GHz. At 10 GHz, the maximum available gain is 17.4 dB. The performance of this device shows that heavily doped channel FET's are very promising for high-frequency operation.     

Low-temperature microwave characteristics of pseudomorphic InxGa1-xAs/In0.52Al0.48Asmodulation-doped field-effect transistors

Low-temperature microwave measurements of both lattice-matched and pseudomorphic In_xGa_1-xAs/In_0.48As (x=0.53, 0.60, and 0.70) channel MODFETs on InP substrates were carried out in a cryogenic measurement system. The measurements were done in the temperature range of 77 to 300 K and in the frequency range of 0.5 to 11.0 GHz at different bias conditions. The cutoff frequency ( f_T) for the In_xGa_1-xAs/In_0.52Al_0.48As MODFETs improved from 22 to 29 GHz, 29 to 38 GHz, and 39 to 51 GHz, for x=0.53, 0.60, and 0.70, respectively, as the temperature was lowered from 300 to 77 K, which is approximately a 31% increase at each composition. No degradations were observed in device performance. These results indicate an excellent potential of the pseudomorphic devices at low temperatures     

YBa2Cu3O7 superconductors forhigh-speed interconnects

The surface resistance of high-quality YBa₂Cu₃ O₇ superconducting films measured over a frequency range from 10 to 500 GHz using high-speed optoelectronic techniques is discussed. A direct comparison is made with the surface resistance of gold and superconducting niobium conductors. Using the measured surface resistance, the propagation characteristic of interconnects based on YBa ₂Cu₃O₇ superconductors at 77 K is simulated and compared to that of gold transmission lines at 77 K and superconducting niobium lines at 7.7 K