High-transconductance heterostructure Ga0.47In0.53As/InP metal-insulator-semiconductor field-effect transistorsgrown by chemical beam epitaxy

SiO₂ insulator is on top of an InP layer; current transport occurs, however, an in adjacent n-type Ga_0.47In_0.53As:Sn layer. A transconductance of g_m=300 mS/mm is obtained from depletion-mode MISFETs with a gate length of 1.2 μm. This MIS (metal-insulator-semiconductor) junction has a symmetric current-voltage characteristic and a low-leakage current of ~1 nA at ±2 V. High-frequency S-parameter measurements performed b probing devices on the wafers yield a unity current gain frequency of F _t=22.2 GHz and a maximum frequency of oscillation f _max=27 GHz     

High-frequency InP/InGaAs double heterojunction bipolar transistorson Si substrate

Self-aligned high-frequency InP/InGaAs double heterojunction bipolar transistors (DHBTs) have been fabricated on a Si substrate. A current gain of 40 was obtained for a DHBT with an emitter dimension of 1.6 μm×19 μm. The S parameters were measured for various bias points. In the case of I_C=15 mA, f _T was 59 GHz at V_CE=1.8 V, and f _max was 69 GHz at V_CE=2.3 V. Due to the InP collector, breakdown voltage was so high that a V_CE of 3.8 V was applied for I_C=7.5 mA in the S-parameter measurements to give an f_T of 39 GHz and an f_max of 52 GHz     

Small-signal characteristics of n+-Ge gate AlGaAs/GaAsMISFET's

The small-signal characteristics have been clarified by S-parameter measurements and equivalent circuit modeling. A large intrinsic transconductance of 630 mS/mm and a maximum cutoff frequence f_T of 70 GHz have been achieved for a MISFET with a gate length of 0.4 μm. The average electron drift velocity in the channel, evaluated from the f_T, was as high as 1.7×10⁷ cm/s. In obtaining an equivalent-circuit model, a gate conductance parallel to the gate-source capacitance is introduced to take into account the gate forward current of normally-off FETs The gate conductance does not cause the f _T of the MISFET to deteriorate due to a small gate forward current at a large gate bias, in contrast to GaAs MESFETs     

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     

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     

Anisotype-gate self-aligned p-channel heterostructure field-effecttransistors

A new self-aligned p-channel HFET structure was evaluated for application to complementary HFET circuits. The AlGaAs/InGaAs HFET structure uses an anisotype graded n⁺ InGaAs/GaAs semiconductor gate to enhance the barrier height of the FET, resulting in a significant reduction in gate leakage current at low voltages. With AlGaAs composition of x=0.3, and a thin AlAs spacer of 60 Å, leakage current was reduced by a factor of about 1000 at gate voltage of 1 V, when compared to AlGaAs/InGaAs HIGFET of aluminum content x=0.75. The anisotype PFET maintains high device transconductance, typically 50 mS/mm for 1.3×10 μm PFETs, high reverse breakdown voltages 9-10 V, and low capacitance. Microwave S -parameter characterization resulted in F_t of 5 GHz for a 1×50 μm PFET     

Comparisons of microwave performance between single-gate anddual-gate MODFETs

Both a 1.2-μm and a 0.3-μm gate length, n⁺-GaAs/InGa/n⁺-AlGaAs double-heterojunction MODFET have been fabricated with single-gate and dual-gate control electrodes. Extrinsic DC transconductance of 500 mS/mm has been achieved from a 0.3-μm single-gate MODFET. The device also has a current gain cutoff frequency f_T of 43 GHz and 14-dB maximum stable gain at 26 GHz with the stability factor k as low as 0.6 from the microwave S-parameter measurements. At low-frequency dual-gate MODFETs demonstrate higher gain than the single-gate MODFETs. However, the k of dual-gate MODFETs approaches unity at a faster rate. Power gain roll-off slopes of 3-, 6-, and 12-dB/octave have been observed for the dual-gate MODFETs     

On-wafer microwave measurement setup for investigations on HEMTsand high-Tc superconductors at cryogenictemperatures down to 20 K

An on-wafer measurement setup for the microwave characterization of HEMTs and high-T_c superconductors at temperatures down to 20 K is presented. Both S-parameter and noise measurements can be performed in the frequency range from 45 MHz to 40 GHz and 2 GHz to 18 GHz, respectively, using standard calibration techniques and commercial microwave probe tips. Microwave measurements on a pseudomorphic FET and an AlGaAs-GaAs HEMT as well as investigations on a superconducting filter are presented to demonstrate the efficiency of the developed system     

A temperature noise model for extrinsic FETs

A resistor temperature noise model for FETs has been successfully applied to extrinsic FETs to predict the frequency dependence of minimum noise figure F_min and associated gain G_Aopt. The model gives a fixed relationship between F_min and G_Aopt with one fitting parameter T_d. An extensive comparison to published results shows that the majority of FETs can be modeled with effective T_d values (the temperature of the output resistor) between 300 and 700 K for all of the frequencies (8 to 94 GHz), gate lengths (0.8 to 0.1 μm), and material types examined. The analysis shows that InP-based MODFETs exhibit significantly lower F_min and higher G_Aopt than conventional and pseudomorphic GaAs-based MODFETs of the same gate length. The results suggest a high F_max is a key factor for low noise figure     

X-band power AlGaAsInGaAs P-n-p HBTs

AlGaAs/InGaAs P-n-p heterojunction bipolar transistors (HBTs) were fabricated using carbon-doped material grown by nonarsine metal-organic vapor-phase epitaxy (MOVPE). F_max of 39 GHz and f_t of 18 GHz were obtained. Operated in common-base mode, a P-n-p HBT achieved 0.5-W output power with 8-dB gain at 10 GHz; saturated output power was 0.69 W. Results are presented for devices with emitter lengths from 120 to 600 μm     

Measurement of the characteristics of the optical-microwavedouble-resonance effect of the 87Rb D1line for application as an atomic frequency standard

The OMDR (optical-microwave double resonance) spectrum of ⁸⁷ Rb with the aim of using a frequency-stabilized GaAs semiconductor laser instead of an Rb lamp as a pumping source in a gas-cell-type Rb frequency standard. Natural isotope ⁸⁷Rb was sealed in a glass cell with buffer gases (Ar/N₂=1.2, total pressure=39 torr). The double resonance signal in the 5P_1/2(F=2)←5S_1/2( F=1) transition appearing at the resonance to the F=2←1 hyperfine transition of the 5S_1/2 state was detected. The optimum operational cell temperature was 56°C. The peak-to-peak frequency width of the atomic hyperfine resonance discriminator used to stabilize the microwave frequency shifts induced by detuning of the laser frequency, changes in the laser and microwave powers, and temperature drift of the cell were investigated     

Co-integration of resonant tunneling and double heterojunctionbipolar transistors on InP

The authors report the first co-integration of resonant tunneling and heterojunction bipolar transistors. Both transistors are produced from a single epitaxial growth by metalorganic molecular beam epitaxy, on InP substrates. The fabrication process yields 9-μm²-emitter resonant tunneling bipolar transistors (RTBTs) operating at room temperature with peak-to-valley current ratios (PVRs) in the common-emitter transistor configuration, exceeding 70, at a resonant peak current density of 10 kA/cm², and a differential current gain at resonance of 19. The breakdown voltage of the In_0.53Ga_0.47As-InP base/collector junction, V_CBO, is 4.2 V, which is sufficient for logic function demonstrations. Co-integrated 9-μm²-emitter double heterojunction bipolar transistors (DHBTs) with low collector/emitter offset voltage, 200 mV, and DC current gain as high as 32 are also obtained. On-wafer S-parameter measurements of the current gain cutoff frequency (f_T) and the maximum frequency of oscillation (f_max) yielded f _T and f_max values of 11 and 21 GHz for the RTBT and 59 and 43 GHz for the HBT, respectively     

DC and microwave characteristics of InAlAs/InGaAssingle-quantum-well MODFETs with GaAs gate barriers

The design and performance of In_0.53Ga_0.47As/In_0.52Al_0.48 As modulation-doped field-effect transistors (MODFETs) have been optimized by incorporating a single In_0.53Ga_0.47As quantum-well channel and a thin strained GaAs gate barrier layer. These help to lower the output conductance and gate leakage current of the device, respectively. The DC performance of 1-μm-gate devices is characterized by extrinsic transconductances of 320 mS/mm at 300 K and 450 mS/mm at 77 K and a best value of f_T=35 GHz is derived from S-parameter measurements     

Quarter-micrometer low-noise pseudomorphic GaAs HEMTs withextremely low dependence of the noise figure on drain-sourcecurrent

Quarter-micrometer pseudomorphic (PM) AlGaAs-InGaAs-GaAs HEMTs with an In mole fraction of 21% have been successfully developed, fabricated, and characterized. The devices are realized in a commercial technology by using a multiple-gate-finger layout with air bridges for the interconnection of the source pads and a Si₃N₄ passivation. PM HEMTs with a gate width of 6×20 μm exhibit state-of-the-art noise figures of 0.65 and 0.82 dB with an associated gain of 14.5 and 11.5 dB at 12 and 18 GHz, respectively. The noise figure shows the lowest dependence on the drain-source current yet reported with ΔF_max<0.12 dB for a wide biasing range from 25% I_dss up to 150% I _dss at 12 GHz when I_dss=170-250 mA/mm     

Vector S-parameter measurements of the superconductingvortex flow transistor

Vector S-parameter measurements of the superconducting vortex flow transistor (VFT) are presented. The measurements were obtained for frequencies up to 100 MHz on VFTs that had a calculated transmit-time cutoff frequency of 5 GHz. An equivalent circuit model that includes calculations of the VFT transresistance, input inductance, and feedthrough capacitance is derived from these measurements. The measurements are limited to an upper frequency of 100 MHz due to crosstalk in the low-impedance system     

Microwave performance of InGaAs/InAlAs/InP SISFETs

Microwave S-parameter measurements and equivalent-circuit modeling of In_0.53Ga_0.47As/In_0.52Al_0.48 As/InP semiconductor-insulator-semiconductor FETs (SISFETs) of 1.1-μm gate length are discussed. The devices incorporated wide-bandgap buffers, self-aligned contact implants, and refractory air-bridge gates. Their DC I-V characteristics displayed sharp pinchoff, good output conductance of 10-20 mS/ss, and extrinsic transconductance up to 220 ms/mm at room temperature. The maximum unity-current-gain frequency was 27 GHz. Gate resistance was found to be the dominant factor limiting microwave power gain     

New method for measuring carrier concentration profile near a GaAssurface through a network analyzer

A method based on S-parameter measurement which precisely obtains the junction capacitance of the Schottky gate of GaAs MESFETs is proposed. In this method the junction capacitance is derived from a diode circuit simulation based on S-parameter measurements. Determination of the junction capacitance under forward-biased voltage and the carrier concentration profile near the channel surface of Schottky gates are possible with this method     

The new two-dimensional electron gas base HBT (2DEG-HBT):two-dimensional numerical simulation

The bipolar/FET characteristics of the 2DEG-HBT are analyzed extensively by a two-dimensional numerical simulator based on a drift-diffusion model. For bipolar operations at high collector current densities, it is confirmed that the cutoff frequency f_T is determined mainly by the collector transit time of holes and by the charging time of the extrinsic base-collector capacitance C _bc^EXT. The charging times of the emitter and base regions and the base transit time are shown to be negligible. A high cutoff frequency F_T (88 GHz) and current gain h_FE (760) are obtained for an emitter size of 1×10 μm², and undoped collector thickness of 150 nm, and a collector current density J_c of 10⁵ A/cm². The FET operation of the same 2DEG-HBT structure shows a threshold voltage V_th of 0.74 V, the transconductance G_m^max of 80 mS/mm, and maximum cutoff frequency F_T^max of 15 GHz. The dependence of the device performance on material parameters is analyzed extensively from a device design point of view     

A linear statistical FET model using principal component analysis

An important issue in statistical circuit design, other than the algorithms themselves, is the development of efficient, statistically valid element models. The authors first discuss what features are needed for a good statistical model. The standard FET model is shown to be difficult to use in a statistical simulation, due to the nonlinear relation between FET S-parameters and model parameters. A linear statistical FET model is then proposed that is based on principal component analysis. This linear model gives uncorrelated model parameters. In an example using measured S-parameter data from ninety 0.5-μm GaAs FETs, 13 uncorrelated model parameters were needed to model the data from 1 to 11 GHz and at one bias. Simulation using this linear model and issues relating to bias are discussed     

A construction of non-Reed-Solomon type MDS codes

A construction is presented of long maximum-distance-separable (MDS) codes that are not generalized Reed-Solomon (GRS) type. The construction uses subsets S,|S|=m of a finite field F=GF(q) with the property that no t distinct elements of S add up to some fixed element of F . Large subsets of this kind are used to construct [n=m+2, k=t+1] non-GRS MDS codes over F