Compensation degradation mechanism for high-efficiency GaAs IMPATT diodes

The reliability of Cr Schottky-barrier high-efficiency (hi-lo) GaAs IMPATTs has been investigated. Devices operated under d.c. conditions degraded due to compensation of the electron concentration in the avalanche region of the devices. This degradation was not observed in diodes oven-tested with no bias applied.     

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.     

A new concept for high-efficiency operation of high-low-type GaAs IMPATT diodes

A new operation mode, the "surfing mode," is proposed as an explanation for the high-efficiency operation of high-low-type GaAs IMPATT diodes. This mode is characterized by the concept that the avalanche charge pulse drifts synchronously with the movement of the front edge of the depletion layer at a velocity higher than the saturation velocity. The design chart of high-low-type GaAs IMPATT diodes is determined on the basis of the concept of the "surfing mode." The high-low-type GaAs IMPATT diodes designed using this chart exhibited output powers of 15.3 W (Delta T_{j}= 210°C) at 6.1 GHz with 25-percent efficiency.     

GaAs IMPATT diodes for 60 GHz

High-performance GaAs double-drift Read IMPATT diodes have been demonstrated at 60 GHz. 1.24-W CW output power at 11.4-percent dc to RF conversion efficiency was obtained with a junction temperature rise of 225°C. The doping profiles and test circuits have not yet been optimized and we expect that still higher power and efficiency should be achievable.     

Comparison of high-efficiency GaAs IMPATT designs

Calculations of maximum generated r.f. powers are presented for GaAs single-drift Read, double-drift Read and hybrid Read structures at 10 GHz. The single-drift Read diode gives the highest output power in c.w. applications, and the double-drift design is superior in pulsed operation.     

Millimeter-wave GaAs Schottky-barrier IMPATT diodes

Recent experimental observations on a Schottky-barrier GaAs IMPATT diode for F-band operation are presented. The diode slices were thinned to 10 to 20 µm by removing the substrate by precision polishing. Output power of 304 mW at 50 GHz with 4.58 percent efficiency was observed. The highest efficiency was 4.72 percent at 55 GHz.     

High-efficiency X-band GaAs IMPATT diodes

Epitaxial GaAs diodes have been fabricated giving 65¹mW CW output power at 10 GHz under room temperature operation. A dc to RF efficiency of 10.1 percent was obtained from a diode operating CW while the measured output of another diode was over 20 mW for 3 mA dc with 70-volt biasing.     

Millimeter-wave GaAs read IMPATT diodes

We have designed, fabricated, and evaluated gallium arsenide Read IMPATT diodes for Ka-band (36-38 GHz)operation. The devices were packaged units intended for manufacturability and high yield. Oscillator output power as high as 710-mW CW was obtained at 9-percent efficiency. This paper describes design and fabrication techniques employed and discusses the potential and limitations of such devices.     

High-efficiency proton-isolated GaAs IMPATT diodes

The fabrication and c.w. operation of planar proton-isolated diffused junction and Schottky-barrier GaAs IMPATT diodes are described. The diodes have shown a maximum efficiency of 13.5% and output power of 315 mW in the Q band. Planar diodes appear to be superior to mesa devices formed from identical material.     

High-efficiency monolithic GaAs IMPATT diodes

Impedance-matching circuits were integrated on the same chip as the IMPATT diodes to produce monolithic impatt diodes for millimetre-wave applications. A drastic reduction of device-to-circuit parasitic elements was achieved by placing the external circuitry very close to the device. Oscillators fabricated in this fashion gave the highest efficiencies reported so far in the 30?35 GHz range with 28% conversion efficiency using hybrid-Read structures.     

Millimeter-wave GaAs distributed IMPATT diodes

Millimeter-wave oscillations were obtained in distributed GaAs IMPATT diodes prepared by molecular beam epitaxy (MBE). Both single-drift-region and double-drift-region structures were used to fabricate various length devices, up to 1.25 mm, to investigate oscillation frequency dependence on device length. Output power levels of 1.5 and 0.5 W were obtained at 22 and 50 GHz, respectively, using 500-ns pulses. The highest frequency of oscillation observed was 89 GHz.     

High-efficiency V-band GaAs IMPATT diodes

Double-drift GaAs IMPATT diodes were designed for V-band frequency operations and fabricated using molecular-beam epitaxy. The diodes were fabricated in two configurations: (a) circular mesa diodes with silver-plated (integrated) heat sinks; (b) pill-type diodes bonded to diamond heat sinks. Both configurations utilised a miniature quartz-ring package. Output power greater than 1 W CW was achieved at V-band frequencies from diodes on diamond heat sinks. The best conversion efficiency was 13.3% at 55.5 GHz with 1 W output power.     

A modified GaAs IMPATT structure for high-efficiency operation

A p⁺-n⁽⁺⁾-n-n⁺just punchthrough IMPATT structure is proposed and analyzed. This high-low junction structure differs from the Read structure in that the carrier concentration in the n-layer is high enough that the breakdown and punchthrough occur at the same time; yet it differs with the regular p⁺-n junction structure in that an additional n⁽⁺⁾-layer with prescribed carrier concentration and layer thickness is present. Tradeoffs between the efficiency and noise of this high-low junction IMPATT are presented and compared to the case of a conventional p-n junction IMPATT. It is shown that either the efficiency or noise performance can be improved, although one at the expense of the other. As an example, the maximum efficiency of a high-low junction IMPATT is improved from about 23 to 30 percent at the expense of a degradation in noise performance of 7 dB. On the other hand, the noise of an X-band diode can be improved by 6 dB with a degradation in efficiency from 23 to 12 percent. This structure should be useful for high-efficiency high-power applications where the noise specifications can be relaxed, or as local oscillators where the noise performance is important.     

Low-frequency high-efficiency oscillations in germanium IMPATT diodes

Pulsed operation of germanium IMPATT diodes has produced oscillations from 10 MHz to 12 GHz, with efficiencies exceeding 40 percent for frequencies between 2 and 3 GHz. Recorded waveforms show that IMPATT oscillations are required to initiate the lower frequency high-efficiency modes. The diodes are epitaxial diffused junction n-p-p⁺mesa structures, with depletion widths ∼ 5 microns and breakdown voltages ∼ 60 volts. Typical diode area is2 times 10^{-4}cm². Static I-V curves, obtained with circuit conditions which do not permit any oscillations, exhibit positive incremental resistance. The usual IMPATT mode would be expected to be between 6 and 12 GHz. Operation at frequencies below the IMPATT frequency requires circuit conditions suitable for IMPATT oscillations to be present to initiate the lower frequency, higher efficiency mode. This mode is characterized by a sudden decrease in diode voltage and a simultaneous increase in current, similar to that reported for silicon devices [1]. Reproducible current and Voltage waveforms have been recorded for four distinctly different low-frequency modes of operation which result only from changes in the ac circuit seen by the diode.     

GaAs 50 GHz Schottky-barrier IMPATT diodes

Technological improvements have been made to realise high-efficiency GaAs Schottky-barrier IMPATT diodes in the 50 GHz band. Efficiency and output power have been increased by a factor of 1.5 over previous best results. Efficiency as high as 11.0% at 51 GHz and an output power of 420 mW at 53 GHz have been obtained.     

140 GHz GaAs double-Read IMPATT diodes

CW GaAs double-Read IMPATT diodes for D-band frequencies are designed and tested. For reproducible RF impedance matching, the module encapsulation technique is applied. Ohmic losses of the active device are reduced by a titanium-Schottky contact instead of an alloyed ohmic n ⁺-contact. At 144 GHz 100 mW RF power with a conversion efficiency of 5% is realised     

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.     

High-power 11 GHz amplifier using high-efficiency IMPATT diodes

The feasibility of using high-efficiency IMPATT diodes in the output stage of a high-power amplifier for 11 GHz digital radio relay systems has been proved with a circuit having a gain of 6dB and an output power of 8.4 W. The circuit used is a troughline version of the `Rucker? combining circuit and contains two diodes in specially designed packages. Error-rate measurements show that negligible degradation is introduced by the amplifier, which can now be seriously considered as a replacement for the travelling-wave tube amplifier.     

Effects of tunneling on high-efficiency IMPATT avalanche diodes

A theoretical and experimental study is presented of the effects of tunnel injection on high-efficiency IMPATT avalanche diodes characterized by a high low-doping profile. Some characteristics usually observed in such high-efficiency IMPATT oscillators are explained, taking into account the effects of tunneling.     

Design considerations of high-efficiency double-drift silicon IMPATT diodes

High-efficiency silicon double-drift IMPATT diodes with a low-high-low doping profile structure are proposed. Devices with efficiencies of 25 percent for 12 GHz, 24 percent for 18 GHz, and 19 percent for 50 GHz, are Predicted by numerical calculations.