Multi-layer epitaxially grown silicon impatt diodes at millimeter-wave frequencies

Complementary (N⁺PP⁺) and double-drift (N⁺NPP⁺) silicon IMPATT diodes were prepared and investigated as oscillators in the millimeter-wave frequency region of 50 to 70 GHz. All the diodes were fabricated from multi-layer epitaxially grown silicon structures. A maximum CW output power level of 198 mW at 62.9 GHz and a maximum conversion efficiency of 7.3% have been measured for the complementary diodes. The double-drift IMPATT diodes have a maximum CW output power of 400 mW at 56.3 GHz and a maximum conversion efficiency of 8.5%.     

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.     

C.W. operation of ion-implanted GaAs read-type IMPATT diodes

Epitaxial and ion-implantation techniques have been combined to form a high/low doping profile for GaAs Schottky-barrier Read-type IMPATT diodes. A c.w. output power of 1.1 W with 25% conversion efficiency was obtained at 11 GHz.     

Physical understanding and optimum design of high-powermillimeter-wave pulsed IMPATT diodes

A physical understanding of the specific mode of operation of high-power millimeter-wave pulsed IMPATT diodes is derived from a self-consistent numerical model. It is shown theoretically that there exists a uniformly avalanching p-i-n-like mode in high-current-density, pulsed silicon double-drift IMPATT diodes, as has been previously suggested. An optimum symmetrical flat doping-profile double-drift structure for 100-GHz operation is presented. It could deliver more than 40 W of available peak power with a 10% conversion efficiency accounting for circuit losses, at a safe junction temperature rise. The theoretical results allow an optimum design of the 94-GHz IMPATT structure for peak output power in excess of 50 W under low duty cycle     

Passivated millimeter-wave silicon IMPATT diodes fabricated by ion implantation

Ion implantation has been combined with planar-mesa processing techniques to realize a passivated silicon IMPATT diode for millimeter-wavelength operation. A continuous-wave output power of 100 mW was obtained at 62 GHz from a fully passivated single-drift-region p⁺-n-n⁺structure.     

High-Power 50-GHz Double-Drift-Region IMPATT Oscillators with Improved Bias Circuits for Eliminating Low-Frequency Instabilities

Low-frequency instabilities in millimeter-wave double-drift-region (DDR) IMPATT diodes are investigated and new oscillator circuits with the improved bias circuits for eliminating the low-frequency instability are developed. DDR IMPATT diodes mounted in these circuits exhibited a maximum free-running oscillation power of 1.6 W at 55.5 GHz with 11.5-percent conversion efficiency. A highly stabilized oscillator was also constructed with the maximum output power of 1 W and the frequency stabflity 0.3 ppm/mA at 51.86 GHz.     

Microstrip Varactor-Tuned Millimeter-Wave IMPATT Diode Oscillators

Varactor-tuned millimeter-wave IMPATT diode oscillators in microstrip form using chip-mounted diodes are described. A nearly level output power of 28 /spl plusmn/ 8 mW was achieved over a 6-GHz tuning range. Tunable bandwidths as high as 8 GHz with 6-26 mW of power were obtained from a single source. P-type epitaxial silicon IMPATT diodes were used for both the active device and the tuning varactor functions.     

Large-signal analysis of Lo-Hi-Lo double-drift silicon IMPATT diodes at 50 GHz

Large-signal analysis of a lo-hi-lo double-drift silicon IMPATT diode at 50 GHz shows that the device is capable of output power of 1.1 W and efficiency of 20 percent for a device area of 2 × 10^-5cm²at a dc biasing current density of 12 kA/cm²and ac voltage amplitude of 12 V. It is also found that, both output power values and efficiencies decrease with increasing enhanced leakage current.     

Millimeter-Wave Silicon IMPATT Sources and Combiners for the 110-260-GHz Range

This paper reports recent progress in CVV and pulsed silicon IMPATT sources in the 110-260-GHz frequency range. Pulsed output power levels of 3, 1.3, and 0.7 W, and CW output power levels of 110, 60, and 25 mW have been consistently achieved from single-drift IMPATT diodes at 140, 170, and 217 GHz, respectively. A Read-type IMPATT diode that generated good output power over a wide frequency range was fabricated. A bridged double-quartz standoff package was developed and successfully used for the entire frequency range. Power combiners at center frequencies of 140 and 217 GHz were developed with peak output power of 9.2 and 1 W, respectively.     

Power-impedance-frequency limitations of IMPATT oscillators calculated from a scaling approximation

The obtainable CW power of silicon IMPATT oscillators, as a function of frequency, is calculated by scaling from reference results. The analysis differs from previous treatments in that the microwave circuit impedance limitation, as observed experimentally, is utilized simultaneously with thermal impedance limitations to uniquely determine device diameter, operating currents, and output power. Results are presented for single and multiple (parallel) units on copper and diamond mounting studs, and for both single (p⁺-n-n⁺) and double-drift-region (p⁺-p-n-n⁺) structures. Obtainable power falls off essentially as 1/f until an ultimate (nonthermal) space-charge-limited current density is reached. Beyond this point the obtainable power varies as f^-2.14. The calculated results on single-drift-region structures are in agreement with experimental observations over the range of frequencies from 13 to 55 GHz, and the analysis predicts an obtainable power of 300 mW at 110 GHz for a double-drift-region structure with 10 percent conversion efficiency.     

Double-drift millimetre-wave IMPATT diodes prepared by epitaxial growth

The preparation of silicon double-drift millimetre-wave IMPATT diodes by the epitaxial growth of n- and p-type layers successively on n-type substrates is described. Carrier-concentration profiles comparable with those reported for double layers formed by ion implantation are obtained; a microwave output power of 560 mW with 11% efficiency has been achieved at 48 GHz.     

Silicon high-resistivity-substrate millimeter-wave technology

The application of molecular beam epitaxy (MBE) and X-ray lithography for the fabrication of monolithic integrated millimeter-wave devices on high-resistivity silicon has been investigated. Process compatibility and the retention of high-resistivity characteristics were measured using the spreading resistance method and Hall measurements after various process steps. Microstrip resonators of ring and linear geometry were fabricated on 10 000 Ω.cm silicon substrates. For linear microstrip resonators, the attenuation was found to be less than 0.6 dB/cm at 90 GHz. A 95-GHz IMPATT oscillator circuit and a planar microstrip antenna array have been fabricated on highly insulating silicon substrates. For the oscillator, a combined monolithic-hybrid integration technique was used to attach the discrete IMPATT diode to the resonator circuit. The oscillator does not require tuning elements. Preliminary experimental results are 8 mW of output power with 0.2 percent efficiency at 95 GHz.     

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.     

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.     

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.     

Ion-implanted planar-mesa IMPATT diodes for millimeter wavelengths

A process has been developed that combines ion-implantation doping with planar and mesa-etching techniques for the fabrication of fully passivated millimeter-wave IMPATT diodes. The device geometry consists of an IMPATT diode surrounded by a two-layer annular region of passivation: one layer of high-resistivity semiconductor and the other of thick insulator material. Devices constructed with this new geometry have sufficient mechanical strength to allow direct mounting into microwave circuits without the use of an insulator standoff and metal ribbon package arrangement. A simple model of the diode-circuit interaction is used to estimate the degradation in microwave performance as a function of the passivation parasitics. These results are compared to a diode with no parasitic losses. Based on the I²-PLASA process, a fully passivated silicon IMPATT diode was fabricated for V-band (50-75-GHz) operation. Degradation factors of approximately 50 percent are predicted for the present devices. A continuous-wave output power of 100 mW was obtained at 62 GHz from an I²-PLASA IMPATT diode with an implanted p⁺-n-n⁺doping profile. Mechanical tuning characteristics of these devices were found to be more broad-band than standard packaged diodes. The measured AM and FM noise spectra close to the carrier were representative of standard single-drift silicon millimeter-wave IMPATT diodes.     

Ion-implanted double-drift Ka-band diodes

The application of a doubly charged boron (¹¹B⁺²) beam to the formation of p-type drift regions in symmetrical Ka-band double-drift silicon IMPATT diodes is discussed. Devices fabricated with these implanted impurity distributions exhibited output powers ∼1.2 W with 10-percent conversion efficiencies over the frequency range of 29 to 39 GHz.     

Large-signal characterization of DDR silicon IMPATTs operating in millimeter-wave and terahertz regime

The authors have carried out the large-signal characterization of silicon-based double-drift region(DDR) impact avalanche transit time(IMPATT) devices designed to operate up to 0.5 THz using a large-signal simulation method developed by the authors based on non-sinusoidal voltage excitation.The effect of band-to-band tunneling as well as parasitic series resistance on the large-signal properties of DDR Si IMPATTs have also been studied at different mm-wave and THz frequencies.Large-signal simulation results show that DDR Si IMPATT is capable of delivering peak RF power of 633.69mW with 7.95% conversion efficiency at 94GHz for 50% voltage modulation,whereas peak RF power output and efficiency fall to 81.08 mW and 2.01% respectively at 0.5 THz for same voltage modulation.The simulation results are compared with the experimental results and are found to be in close agreement.     

Potentials of GaP as millimeter wave IMPATT diode with reference to Si, GaAs and GaN

This paper presents the simulation results of DC,small-signal and noise properties of GaP based Double Drift Region( DDR) Impact Avalanche Transit Time( IMPATT) diodes. In simulation study we have considered the flat DDR structures of IMPATT diode based on GaP,GaAs,Si and GaN( wurtzite,wz) material. The diodes are designed to operate at the millimeter window frequencies of 94 GHz and 220 GHz. The simulation results of these diodes reveal GaP is a promising material for IMPATT applications based on DDR structure with high break down voltage( V_B) as compared to Si and GaAs IMPATTs. It is also encouraging to worth note GaP base IMPATT diode shows a better output power density of 4. 9 × 10~9 W/m~2 as compared to Si and GaAs based IMPATT diode. But IMPATT diode based on GaN( wz) displays large values of break down voltage,efficiency and power density as compared to Si,GaAs and GaP IMPATTs.     

Millimeter-Wave Device Technology

We have investigated novel techniques for the fabrication of silicon IMPATT diodes for use at frequencies of 220 GHz and beyond. We report on diodes yielding 25 mW CW at 102 GHz with 2-percent conversion efficiency, and 16 mW CW at 132 GHz with 1-percent conversion efficiency. The basic techniques described are ion implantation, laser annealing, unique secondary-ion mass spectrometry (SIMS) profile diagnostics, and novel wafer thinning, yielding ultrathin, reproducible wafers. The utilization of these technologies, as they are further refined, can result in the development of silicon monolithic integrated sources.