New insulated-gate inverted structure AlGaAs/GaAs/n-AlGaAs HEMT ring oscillator

Inverted-structure high electron mobility transistors with insulated-gate structure, i.e. AlGaAs/GaAs/n-AlGaAs, have been successfully applied to E/D-type DCFL ring oscillators. High transconductance of 280 mS/mm was obtained at 77 K in an enhancement-mode FET with 0.8 ?m gate length. Gate leakage current was small enough even at a gate voltage of +1.4 V both at 300 K and 77 K, and a high logic swing of more than 1 V was achieved using a DCFL inverter. A 21-stage ring oscillator showed a minimum gate delay as small as 18.0 ps with power dissipation of 520 ?W/gate at 77 K.     

A low-power GaAs front-end IC with current-reuse configurationusing 0.15-μm-gate MODFETs

We have developed a novel current-reuse configuration of a front-end integrated circuit (IC), where the current can be reused in the whole circuit blocks that are a low-noise amplifier, local amplifier, and mixer. The power dissipation of the front-end IC is reduced by the factor of three as compared to conventional front-end ICs. Excellent RF performance such as conversion gain of 30 dB and noise figure of 1.6 dB at 1.5 GHz is attained under the conditions of the supply voltage and current of 3.6 V and 3 mA, respectively     

Determination of AlGaAs/GaAs HEMT parasitic resistances

An improved technique has been developed to measure source and drain parasitic resistances of AlGaAs/GaAs HEMTs. Similar to the measurement technique typically used for MESFETs, a positive d.c. gate crowding current is applied. Because of the structure of the HEMT, this gate current must be kept very small in order to prevent significant leakage into the AlGaAs layer, which would result in current paths not present in normal operation of the device. The small d.c. gate current necessary to limit the current in this leakage path did not yield a usable signal-to-noise ratio of the measured gate-source, gate-drain and drain-source voltages needed to calculate the parasitic resistances. To overcome this problem, modulation of the drain current with a low-frequency a.c. signal coupled with lock-in techniques to measure the desired voltages was implemented. The resulting improvement in signal-to-noise ratio has made the gate crowding technique suitable for measuring the parasitic resistances of AlGaAs/GaAs HEMTs.     

Comparison of OMVPE Grown GaAs/AlGaAs and GaAs/InGaP HEMT and PHEMT structures

Symmetric δ-doped InGaP and AlGaAs PHEMT structures have been grown by organometallic vapor phase epitaxy with properties that approach those of MBE grown AlGaAs structures. The 300 and 77K carrier concentrations for the InGaP PHEMT were 2.72 and 2.56 × 10¹² cm^{2 −2} and the mobilities were 5,920 and 22,000 cm^{2 2}/V.s. These excellent values suggest that problems associated with switching the anion at the channel heterojunction have been overcome. The corresponding values for the AlGaAs PHEMT were 2.51 and 2.19 × 10¹² cm^{2 −2} and 6,500 and 20,400 cm²/V.s. The uniformity in the indium concentration in the InGaAs layer as determined by photoluminescence, photoreflection, double crystal x-ray diffraction, and Rutherford backscattering was found to be good, but the percent In in the AlGaAs pseudo-morphic high electron mobility transistor (PHEMT) was less than that in the InGaP PHEMT even though the programmed values were the same. The uniformity in the doping distribution as determined by secondary ion mass spectroscopy and electrochemical capacitance-voltage measurements was found to be good, but it decreased with distance from the center of the susceptor. Also, most of the dopants in the δ-doped InGaP and AlGaAs layers were activated.     

10-μm GaAs/AlGaAs multiquantum well scanned array infraredimaging camera

A long-wavelength infrared imaging camera that uses a GaAs/Al_xGa_1-xAs quantum-well infrared photodetector (QWIP) array is demonstrated. Excellent noise equivalent temperature difference sensitivity (NEΔT<0.1°C) has been achieved. The long-wavelength cutoff for the QWIP used in this camera is at λ _c=10.7 μm with the peak response being at λ_p =9.8 μm. A peak detectivity of 2×10¹⁰ cm√Hz/W has been achieved at 77 K as well as an excellent pixel-to-pixel uniformity of 2%. Since GaAs has a more mature growth and processing technology as well as higher uniformity than HgCdTe, it shows great promise for the fabrication of large two-dimensional arrays     

Two-Dimensional Simulation of Interface States Effect on AlGaAs/GaAs HEMT

In most heterostructures there are various interface states due to lattice mismatch or imperfections at the interface.The properties of an AlGaAs/GaAs interface are intimately related to the device performance.The existence of interface states in an Al.Ga,-.As/GaAs heteros...     

A new fabrication technology for AlGaAs/GaAs HEMT LSIs using InGaAsnonalloyed ohmic contacts

The authors studied the nonalloyed ohmic characteristics of HEMTs (high electron mobility transistors). At high integration levels, nonalloyed ohmic contacts were found to have two advantages: an extremely short ohmic length with low parasitic source series resistance and direct connection between the source/drain and gate with the same metal. The propagation delay in a ring oscillator with a single-metal source/drain and gate formed simultaneously was 37 ps/gate (L _g=0.9 μm). The very short ohmic metal contacts and just three contact holes made it possible to reduce the memory cell area greatly. The cell is 21.5×21.5 μm², one of the smallest ever reported for a GaAs-based static RAM. Using smaller load HEMTs or resistor loads in the memory cell, combined with nonalloyed ohmic technology with quarter- or subquarter-micrometer-gate HEMTs it is possible to fabricate a very-high-speed LSI such as a 64-kb static RAM with a reasonable chip size     

A 0.4-μm gate-length AlGaAs/GaAs P-channel HIGFET with 127-mS/mmtransconductance at 77 K

WN-gate, p-channel AlGaAs-GaAs heterostructure insulated-gate field-effect transistors (HIGFETs) fabricated on a metalorganic vapor-phase epitaxy (MOVPE) wafer are discussed. A self-aligned Mg ion implantation (80 keV, 6×10¹³ cm^-2) annealed at 850°C in an arsine atmosphere and the control of the SiO₂ sidewall dimensions allow the fabrication of p-channel HIGFETs with a gate length smaller than 0.5 μm with low subthreshold current. P-channel HIGFETs with 0.4-μm gate lengths exhibit extrinsic transconductances as high as 127 mS/mm at 77 K and 54 mS/mm at 300 K     

A high-gain, low-noise 1/2-μm pulse-doped pseudomorphic HEMT

A 1/2-μm gate-length pulse-doped pseudomorphic high-electron-mobility transistor (HEMT) grown by MBE, which exhibits a current-gain cutoff frequency of 62 GHz, is discussed. The maximum available gain cutoff frequency was greater than 150 GHz. A minimum noise figure of 0.85 dB and associated gain of 14 dB were measured at 10 GHz. Tuned small-signal gain in a waveguide-to-microstrip test fixture at 44 GHz was 7.6 dB. When the HEMT was tuned for power, 260 mW/mm with 5-dB gain and 17% power-added efficiency were obtained at 44 GHz. These results suggest that a 1/2-μm pseudomorphic HEMT is a viable candidate for Q-band applications     

20-40 Gb/s 0.2-μm GaAs HEMT chip set for optical data receiver

Using our 0.2-μm AlGaAs-GaAs-AlGaAs quantum well high electron mobility transistor (HEMT) technology, we have developed a chip set for 20-40 Gb/s fiber-optical digital transmission systems. In this paper we describe five receiver chips: a limiting amplifier with a differential gain of 17 dB and a 3 dB bandwidth of 29.3 GHz, a 40 Gb/s clock recovery, a data decision and a 1:4 demultiplexer, both for bit rates of more than 40 Gb/s, and a static 1:4 divider with operating frequencies up to 30 GHz. All presented chips were characterized on wafer with 50-Ω coplanar test probes     

Dual bridge 6 Gsample/s track and hold circuit inAlGaAs/GaAs/AlGaAs HEMT technology

A T&H circuit with a sampling rate of 6 Gsample/s has been experimentally demonstrated in AlGaAs/GaAs/AlGaAs HEMT technology. The circuit utilises a dual bridge topology suitable for interleaved ADC circuits, doubling the effective sampling rate with an insignificant increase in area compared to the previously reported solutions     

A 3-V 0.5-μm CMOS A/D audio processor for a microphone array

A 0.5-μm 3-V CMOS mixed-mode audio processor is presented. It is mainly composed of 11 low-noise input channels and a dedicated digital audio processor. Analog input signals are provided through an 11-microphone array. The chip size is about 50 mm², and the power dissipation is less than 100 mW. This circuit is dedicated to multimedia applications     

A superlattice GaAs/InGaAs-on-GaAs photodetector for 1.3-μmapplications

A metal-semiconductor-metal detector with a InGaAs/GaAs superlattice active layer showing efficient photoresponse up to 1.35 μm is discussed. The active layer with an In composition of approximately 64% is grown by molecular beam epitaxy on a GaAs substrate at 460°C. The large size detector (200×200 μm²) shows bias-dependent DC gain, fast response speed (FWHM <50 ps), and reasonably low dark current     

An 18-34-GHz dynamic frequency divider based on 0.2-μmAlGaAs/GaAs/AlGaAs quantum-well transistors

The design and performance of a dynamic frequency divider was presented. This digital IC demonstrates the ability of the authors' AlGaAs/GaAs/AlGaAs quantum-well FETs with gate lengths of 0.2 μm. Stable operation was achieved in the frequency range from 18 GHz up to 34 GHz with a power consumption of 250 mW. To the authors' knowledge, this is the best result ever reported for HEMT circuits, and is similar to the frequency limit achieved by use of AlGaAs/GaAs HBTs     

Monolithic V-band frequency converter chip set development using0.2 μm AlGaAs/InGaAs/GaAs pseudomorphic HEMT technology

Monolithic approaches of the development to V-band frequency converters have the advantages of lighter weight and lower cost over conventional hybrid approaches for high volume insertions into satellite communication systems. This paper presents the design, fabrication, and performance of a monolithic V-band frequency converter chip set using 0.2 μm AlGaAs/InGaAs/GaAs pseudomorphic HEMT technology. This chip set consists of three monolithic macrocells and a microcell: an upconverter, a downconverter, and a frequency multiplier for LO signal. A monolithic balanced amplifier microcell is also used to form the LO chain. Individual components, including amplifiers, mixer, and frequency doublers are also described. The superb measured results obtained from this chip set show great promise of the MMIC insertions for the system applications, and represent state-of-the-art performance of MMIC at this frequency     

17 GHz broadband amplifier with 25 dB gain using a 0.3 μmAlGaAs/GaAs/AlGaAs HEMT technology

A broadband amplifier chip based on AlGaAs/GaAs/AlGaAs quantum well FETs with 0.3 μm gate length has been designed and fabricated. The amplifier can be operated with single-ended or differential inputs with an input resistance of 50 Ω. The output signals are differential with both internal load resistances at 100 Ω, the chip area is 1×1 mm², and the power consumption is ~375 mW     

GaAs/AlGaAs and InGaAs/AlGaAs MODFET inverter simulations

Although MODFET's have exhibited the fastest switching speed for any digital circuit technology, there is as yet no clear consensus on optimal inverter design rules. We therefore have developed a comprehensive MODFET device model that accurately accounts for such high gate bias effects as transconductance degradation and increased gate capacitance. The device model, which agrees with experimental devices fabricated in this laboratory, is used in the simulation of direct-coupled FET logic (DCFL) inverters with saturated resistor loads. Based on simulation results, the importance of large driver threshold voltage not only for small propagation delay times but for wide logic swings and noise margins is demonstrated. Furthermore, minimum delay times are found to occur at small supply voltages as seen experimentally. Both of these results are attributed to the reduction of detrimental high gate bias effects. The major effect of reducing the gate length on delay time is to decrease the load capacitance of the gate. Using 0.25-µm gates, delay times of 5 and 3.6 ps at 300 and 77 K, respectively, are predicted. Finally, the recently introduced In-GaAs/AlGaAs MODFET's are shown to have switching speeds superior to those of conventional GaAs/AlGaAs MODFET's.     

Delay time analysis for 0.4- to 5-μm-gate InAlAs-InGaAs HEMTs

InAlAs-InGaAs HEMTs with 0.4- to 5-μm gate lengths have been fabricated and a maximum f_T of 84 GHz has been obtained by a device with a 0.4-μm gate length. A simple analysis of their delay times was performed. It was found that gradual channel approximation with a field-dependent mobility model with E_c of 5 kV/cm holds for long-channel devices (L _g>2 μm), while a saturated velocity model with a saturated velocity of 2.7×10⁷ cm/s holds for short-channel devices (L_g<1 μm)     

Electrochemical capacitance-voltage profiling of the free-carrier concentration in HEMT heterostructures based on InGaAs/AlGaAs/GaAs compounds

The depth distribution of free carriers over the HEMT structures with quantum-well layers is studied by electrochemical capacitance-voltage profiling. It is shown that the actual distribution of the concentration of free carriers and their energy spectrum in the HEMT structure channel can be obtained by numerical simulation of the results of profiling based on the self-consistent solution of one-dimensional Schrödinger and Poisson equations.