Performance of P-type epitaxial silicon millimeter-wave IMPATT diodes

A series of p-type IMPATT diodes (p⁺pn⁺) have been fabricated from epitaxially grown silicon for operation as oscillators at Ka-band frequencies. A maximum CW output power level of 700 mW at 29.6 GHz, a maximum conversion efficiency of 10.9 percent, and a minimum FM noise parameter, M, of 25 dB have been measured on this series of p-type diodes. A diode oscillating in a variable height radial disk cavity was frequency tuned from 27.5 to 40 GHz, covering the entire Ka-band, with a 1.4 dB power variation over the tuning range. The minimum CW output power of this tunable oscillator was 360 mW at 6.5 percent efficiency.     

Design considerations of high-efficiency GaAs IMPATT diodes

The efficiency and noise of p⁺n1n2n⁺GaAs IMPATT diodes have been studied as functions of the doping ratio n1/n2(when n1=n2we have a conventional abrupt p-n junction). For n1/n2>1 there are tradeoffs between efficiency and noise. At 12 GHz, for example, with a ratio of 4 the efficiency is 25 percent and the noise measure is 3 dB higher then that of a conventional IMPATT diode.     

20-GHz high-power GaAs DDR-IMPATT diodes with a p+-p-n-n+structure

GaAs DDR (double-drift-region)-IMPATT diodes have been made by using epitaxial wafers with a p⁺-p-n-n⁺structure, which was made by successive liquid-phase epitaxy of p⁺, p, and n layers on n⁺substrate in one heat cycle. On the diodes with copper heat sink, the maximum CW output power of 1.2 W was obtained at 21 GHz with the efficiency of 15.6 percent.     

Noise characteristics of GaAs and Si IMPATT diodes for 50-GHz range operation

Direct comparison of noise behaviors between GaAs Schottky-barrier junction and Si diffused p⁺-n junction diodes operating in the 50-GHz range is reported by using the same circuitry. In the oscillator operation, the GaAs diode exhibits excess "1/f^m" noise near carrier, whereas the Si diode shows flat spectrum. Far from the carrier, and AM-DSB-NSR of -133 dB in a 100-Hz bandwidth and an FM noise measure of 27.1 dB are observed for GaAs diodes. Corresponding values obtained for Si diodes are -125 and 36.2 dB, respectively. As a reflection amplifier, minimum noise figures of 27.5 and 38 dB are achieved for the GaAs and Si devices, respectively. These results indicate that the GaAs IMPATT is superior in noise behavior to the Si diode also in the 50-GHz frequency range by about 10 dB. It is emphasized that the noise induced in the bias circuit of the IMPATT oscillator is a replica of the sideband noise of the output power and can be used as an indicator to obtain a low-noise tuning condition of the oscillator.     

MOVPE-grown millimeter-wave InGaAs mixer diode technology andcharacteristics

The merits of InGaAs-based millimeter-wave mixer diodes are explored experimentally and theoretically. Schottky junctions on InGaAs exhibit barriers (φ_b) in the neighborhood of 0.25 eV. The high mobility of InGaAs contributes to the low n⁺ sheet resistances of 1.9-5 Ω/square for 1-μm n⁺ InGaAs layers (n_s=1.5×10¹⁹ cm^-3, μ _n=1800 cm²/V·s) grown with our in-house Metalorganic Vapor Phase Epitaxy (MOVPE) system, The design, material growth, fabrication, and characterization of InGaAs integrated mixer/antennae are reported. Pt plating technology, adapted here for InGaAs Schottky contacts, has improved the ideality factor (η) and yield relative to conventional evaporated Pt. With 810 μW of local oscillator power, applied to the diode, and zero DC bias, an integrated InGaAs mixer/antenna demonstrated an excellent diode performance of 199 K RF input double-sideband noise temperature with a corresponding single-sideband (SSB) conversion loss (L_c) of 5.0 dB at LO, RF, and IF frequencies of 94 GHz, 94 GHz±1.4 GHz, and 1.4 GHz, respectively. Likewise, the diodes in an InGaAs subharmonic integrated mixer/antenna demonstrated an equivalent RF-port double-sideband (DSB) noise temperature (T_mix) of 1058 K and single-sideband conversion loss of 10.2 dB at 180 GHz with a 90-GHz LO power (PLO) of 1.6 mW. Compared to GaAs diodes with RF coupling and IF losses removed, the single-ended InGaAs noise temperature results were within 46-100 K of those for state-of-the-art GaAs mixer diodes while requiring significantly less LO power     

High performance millimetre Ge-GaAs mixer diode for low l.o. power applications

Epitaxial Ge/GaAs low-barrier-height Ti-Mo-Au Schottkybarrier diodes exhibit a noise figure of 6.5 dB at 36 GHz and at 0.75 mW of local oscillator (l.o.) power. These diodes represent significant improvement over standard GaAs-Ti diodes at low power levels.     

High-speed DCFL circuits with very shallow junction GaAs JFETs

High-speed DCFL (direct-coupled FET logic) circuits implemented with advanced GaAs enhancement-mode J-FETs are discussed. A divide-by-four static frequency divider operates at up to 6 GHz with a power consumption of 20 mW/flip-flop. A high channel concentration of more than 1×10¹⁸ cm^-3 together with a very shallow junction depth of less than 30 nm for the p⁺-gate results in a transconductance as high as 340 mS/mm at a gate length of 0.8 μm. Open-tube diffusion of Zn using diethylzinc and arsine makes it possible to control a very shallow p⁺-layer less than 10 nm thick. The propagation delay time, as measured with a ring oscillator, was 22 ps/gate with a power consumption of 0.42 mW/gate     

A Millimeter-Wave Quadruple and an Up-Converter Using Planar-Diffused Gallium Arsenide Varactor Diodes

A millimeter-wave quadruple, employing planar-diffused GaAs varactor diodes and a tuned second-harmonic idler circuit, is described. This quadruple operated at an output frequency of 50.4 GHz, produced a maximum power output greater than 13 mW, and exhibited a maximum overall conversion efficiency of 12 percent. 2) A millimeter-wave up-converter using similar diffused GaAs diodes has been operated successfully. The input was at 1.3 GHz, the output at 51.7 GHz, and the local oscillator power was supplied at 50.4 GHz. The minimum observed overall conversion loss, 50.4 to 51.7 GHz, was about 2.5 dB at an output power between 1 and 3 mW. 3) The performance of these devices is described as a function of the parameters of the diodes employed, and a comparison of the performance of diffused-junction and Schottky-barrier diodes (of comparable quality) in the two circuits is discussed. 4) The fabrication and characterization of the planar-diffused gallium arsenide varactor diodes used in these circuits is described; zero-bias cutoff frequencies to values in excess of 2000 GHz were achieved.     

Design considerations of low-noise high-efficiency silicon IMPATT diodes

The noise and efficiency of p⁺-n1-n2-n⁺and n⁺-p1- p2-p⁺high-low silicon IMPATT diodes have been studied as a function of doping ratio n1/n2or p1/p2. In contrast to GaAs IMPATT diodes whose efficiency can be improved with some degradation of noise performance, both the efficiency and noise of Si IMPATT diodes can be improved. As an example, for a 6-GHz silicon n⁺-p1-p2-p⁺IMPATT structure with a doping ratio of 10, the efficiency is 21 percent and the incremental noise as compared to a uniformly doped structure is about -6 dB. These results indicate that silicon high-low structures can compete favorably with GaAs structures in both efficiency and noise performances.     

100 Å-thick tunnel junction by double impurity doping liquid phase epitaxy for V-band TUNNETT oscillation

The tunnel injection transit time (TUNNETT) diodes with p⁺p⁺n⁺n⁻n⁺ structure were fabricated by liquid phase epitaxy (LPE). About 100 Å tunnel junction (p⁺n⁺) was successfully prepared by the double impurity diffusion of Ge and S during LPE growth. Continuous wave (CW) oscillation was realized at 51.520 GHz in the V-band cavity with the phase noise of −60 dBc/Hz at 1 kHz bandwidth.     

Performance and reliability of an improved high-temperature GaAs Schottky junction and native-oxide passivation

We have developed a reliable, high-performance, batch-processed, GaAs tantalum Schottky diode (with a gold overlayer) and native-oxide passivated junction¹in a quasi-planar configuration, Varactors and mixers have been fabricated with near-ideal characteristics and state-of-the-art performance. Typically, they exhibit, at 0 V, a junction capacitance near 0.1 pF and a cutoff frequency in excess of 700 GHz when measured at 55 GHz. In a paramp application pumped at 101 GHz, and a signal frequency of 35 GHz, we have obtained a noise figure of 3.5 dB, a gain of 17 dB, and a bandwidth of 600 MHz. When used as frequency doublers (50-100 GHz) and triplers (35-105 GHz), we have realized better than 25-percent efficiency. As mixers, atXband, we achieved a single sideband noise figure of 6 dB and the diodes are typically able to sustain short pulse energy (1.5 × 10^-9s) of up to 4.5 ergs with no performance degradation. Reliability tests results to date indicate a MTBF of better than 10⁸h at 100°C and greater than 10⁵h at 200°C. In a commercial application of paramps (3.7-4.2 GHz), these diodes have successfully completed 2.5 million operational varactor hours with no performance degradation.     

Near state-of-the-art power in p+-n-n+D-band IMPATT diode on a wafer with ramped n-n+interface

Fabrication of near state-of-the-art (P0= 110 mW, η = 4.85 percent p⁺-n-n⁺D band (f = 124 GHz) Si IMPATT diode on a wafer with ramped n-n⁺interface is described. Introduction of a critical annealing step, prior to p⁺diffusion, in the fabrication sequence of the diode has been found to yield the above results. Possible reasons for power and efficiency enhancement has been discussed.     

An experimental study on improvement of performance for hemispherically shaped high-power IRED's with Ga1-xAlxAs grown junctions

This paper describes the structure and performance of a high-power infrared emitting diode (IRED) designed as a high speed optical beam source for optoelectronic applications. The heterostructured junction is formed on a thick Ga1-xAlxAs liquid phase epitaxy (LPE) grown layer which is used to shape hemispherical emitting surfaces. Dislocation density in recombination region was considerably decreased by the thick layer growth on a GaAs wafer used as a primary substrate. Under dc operations, external quantum efficiencies of around 45 percent at a current density of 0.6 kA/cm²and about 110 mW of optical output power at 200 mA (1 kA/cm²) have been obtained from the diodes with a 160-µm junction diameter. The tendency to reach power saturation with increased current has been decreased by means of reducing of thermal resistance of the mount, and the diodes with 240- µm junction diameter have shown about 180 mW at 600 mA dc and 1.4 W at a 4-A pulse (60 Hz, 50 µs). A large improvement in high frequency response has been obtained and the bandwidth at -3-dB intensity has reached above 120 MHz.     

150 GHz GaAs MITATT source

The performance of a GaAs Schottky barrier transmit-time source is described. The device is reversed biased into mixed tunnel-avalanche breakdown. A CW output power of 3 mW with 1/2% conversion efficiency has been measured at 150 GHz. This is the highest frequency CW GaAs source built to date and has many potential applications in systems requiring a low noise local oscillator in near millimeter microwave integrated circuits.     

GaAs TUNNETT diodes on diamond heat sinks for 100 GHz and above

Single-drift GaAs TUNNETT diodes were mounted on diamond heat sinks for improved thermal resistance and evaluated around 100 GHz in a radial line full height waveguide cavity. The diodes were fabricated from MBE-grown material originally designed for diodes that operate in CW mode around 100 GHz on integral heat sinks. An RF output power of more than 70 mW with a corresponding DC to RF conversion efficiency of 4.9% was obtained at 105.4 GHz. This is the first successful demonstration of GaAs TUNNETT diodes mounted on diamond heat sinks. To the authors' knowledge, these DC to RF conversion efficiencies and RF power levels are the highest reported to date from TUNNETT diodes and exceed those of any single discrete device made of group III-V materials (GaAs, InP, etc.) at this frequency. Free-running TUNNETT diode oscillators exhibit clean spectra with an excellent phase noise of less than -94 dBc/Hz, measured at a frequency off-carrier of 500 kHz and an RF output power of 40 mW     

Fabrication and noise performance of high-power GaAs IMPATTS

Schottky-barrier GaAs IMPATT diodes have been fabrirated in a double epitaxial layer structure on low-etch-pit density substrates. The resulting low defect density in the active region permits high power outputs and low noise measure. Mounted on copper studs and a 20°C heat sink, such diodes have given a maximum CW power output of 2.94 W at 6.1 GHz with 13.8 percent efficiency. The small-signal amplifier noise measure was 25dB. Operated as injection-locked oscillators, the noise measure was 32 dB at an output of 1 W. These results show that in a suitable structure, GaAs can surpass the efficiency and noise performance of other materials, and demonstrate the capability of high power output in this frequency band.     

Beam-lead Schottky-barrier diodes for low-noise integrated microwave mixers

This paper describes the fabrication and performance of beam leadnonn^{+}silicon-molybdenum, barrier dual Schottky diodes. The fabrication is by a process sequence which allows the use of a single molybdenum gold-metal deposition step for both the Schottky barrier and beam-lead interconnection system. TypicalI-Vand1/C^{2}-Vplots indicate uniformity of barrier heigh and n factor. Values of n less than 1.1 were measured with the barrier height at 0.61 eV. Measurements of change in barrier height with temperature up to 500°C show less than ± 10 mV variation. Dc characteristics of these devices give forward current matching of ± 10 mV at 1 mA. The Rsis 10 ohms and the Cjis less than 0.3 pF, giving an RC product less than 3 × 10^-12seconds. Using these devices in a chrome-gold on alumina microstrip integrated mixer, overall single sideband noise figures of 6.5-7.0 dB were measured, with a 1.5 dB IF noise figure, at 9.4 GHz. Measured noise figure was essentially constant over a range of 1-10 mW of local oscillator power, and the diodes will with stand over 500 mW CW RF power. These values compare favorably with discrete packaged devices. Fabrication in series pairs, matched quads or other configurations can be accomplished with good uniformity.     

Low noise, high efficiency GaAs IMPATT diodes at 30 GHz

Low noise, very high efficiency IMPATT diodes provide an attractive alternative to Gunn diodes for many millimetre-wave applications. GaAs hi-lo single-drift IMPATT diodes are demonstrated. The diodes are fabricated using molecular beam epitaxy and (at approximately 30 GHz) exhibit exceptional efficiencies (>20%), very low FM noise (-88 dBc/Hz at 100 kHz off-carrier) and simultaneous CW power levels in excess of 300 mW.<>     

2.5-THz GaAs monolithic membrane-diode mixer

A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5-THz Schottky diode mixer. The mixer blends conventional machined metallic waveguide with micromachined monolithic GaAs circuitry to form, for the first time, a robust, easily fabricated, and assembled room-temperature planar diode receiver at frequencies above 2 THz. Measurements of receiver performance, in air, yield at T_receiver of 16500-K double sideband (DSB) at 8.4-GHz intermediate frequency (IF) using a 150-K commercial Miteq amplifier. The receiver conversion loss (diplexer through IF amplifier input) measures 16.9 dB in air, yielding a derived “front-end” noise temperature below 9000-K DSB at 2514 GHz. Using a CO₂-pumped methanol far-infrared laser as a local oscillator at 2522 GHz, injected via a Martin-Puplett diplexer, the required power is ≈5 mW for optimum pumping and can be reduced to less than 3 mW with a 15% increase in receiver noise. Although demonstrated as a simple submillimeter-wave mixer, the all-GaAs membrane structure that has been developed is suited to a wide variety of low-loss high-frequency radio-frequency circuits