High-performance oscillators and power combiners with InP Gunn devices at 260-330 GHz

InP Gunn devices with graded doping profiles were evaluated for second-harmonic power extraction above 260 GHz. The best devices generated radio frequency(RF) output power levels of 3.9 mW at 275 GHz, 4.8 mW at 282 GHz, 3.7 mW at 297 GHz, 1.6 mW at 329 GHz, and 0.7 mW at 333 GHz with corresponding dc-to-RF conversion efficiencies of 0.24%, 0.31%, 0.32%, 0.19%, and 0.07%. The highest observed second-harmonic frequency was 345 GHz. Two devices each in an in-line power combining circuit generated 6.1 mW at 285 GHz and 2.7 mW at 316 GHz with combining efficiencies of more than 65%.     

High Peak Pulse Power Silicon Double-Drift IMPATT Diodes

The performance of high peak pulse power silicon double-drift IMPATT devices operated at medium pulse repetition frequency are discussed. Several devices were characterized and achieved more than 45-W peak pulse power with 10-percent duty cycle at 9.7 GHz. Conversion efficiencies in the order of 9.7-11.2 percent were observed. These results compare with previously reported 19-W peak power, 10-percent duty-cycle, and 9.5-percent efficiency.     

A study of the power handling ability of gallium arsenide and silicon,single and double drift IMPATT diodes

The concept of a critical current density effect on the operation of silicon and gallium arsenide IMPATT diodes is examined using large signal analysis. This critical current density effect does not appear to exist in the form that is generally thought of to-date. However, other physical processes develop at high current densities which gradually degrade diode efficiencies. These processes are worse in silicon diodes than in gallium arsenide diodes because at a given frequency of operation silicon diodes need a lower doping density than gallium arsenide diodes due to the lower saturated drift velocities of carriers in gallium arsenide. Reasons are suggested which explain why these other processes develop before a true critical current density limit is seen. New scaling data for limits on power handling ability vs frequency of gallium arsenide IMPATT diodes are presented. In addition the advantages of double drift structures over single drift structures are re-examined in the light of the suggestion that silicon and gallium arsenide IMPATT diodes are thermally and impedance limited rather than current density limited at high frequencies. The problem of tunnelling is also examined and is shown to be unimportant at all frequencies up to 120 GHz.     

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.     

Indium gallium arsenide microwave power transistors

Depletion-mode InGaAs microwave power MISFETs with 1-μm gate lengths and up to 1-mm gate widths have been fabricated using an ion-implanted process. The devices employed a plasma-deposited silicon/silicon dioxide gate insulator. The DC current-voltage (I -V) characteristics and RF power performance at 9.7 GHz are presented. The output power, power-added efficiency, and power gain as a function of input power are reported. An output power of 1.07 W at 9.7 GHz with a corresponding power gain and power-added efficiency of 4.3 dB and 38%, respectively, was obtained. The large-gate-width devices provided over twice the previously reported output power for InGaAs MISFETs at X-band. In addition, the first report of RF output stability of InGaAs MISFETs over 24 h period is also presented. An output power stability within 1.2% over 24 h of continuous operation was achieved. In addition, a drain current drift of 4% over 10⁴ s was obtained     

High-power high-efficiency c.w. Gunn oscillators in X band

Gunn oscillators on diamond heat sinks have produced up to 780 mW c.w. with 5.1% efficiency at 9.9 GHz. The devices were operated in full-height waveguide cavities. Similar devices on copper have produced up to 700 mW with 4.1% efficiency and typical powers of 600 mW with efficiencies of 3.9%. The effect of varying the 2nd-harmonic loading on devices mounted in fully-reduced-height waveguide has also been investigated, but no enhancement in output power at the fundamental frequency was observed.     

A Power Silicon Microwave MOS Transistor

Vertical MOS silicon power transistors for microwave power applications have been fabricated using an angle evaporation technique to position the gate electrode on the side of a mesa. These devices have produced 3-W output power at 1.5 GHz as a Class B amplifier and exhibit excellent linearity and noise properties. Device modeling has shown that parasitic capacitances are the chief factor limiting the frequency response, and the prospects for useful devices at 4 GHz are good.     

A study of frequency response in silicon heterojunction bipolartransistors with amorphous silicon emitters

A detailed physical model of amorphous silicon (a-Si:H) is incorporated into a two-dimensional device simulator to examine the frequency response limits of silicon heterojunction bipolar transistors (HBT's) with a-Si:H emitters. The cutoff frequency is severely limited by the transit time in the emitter space charge region, due to the low electron drift mobility in a-Si:H, to 98 MHz which compares poorly with the 37 GHz obtained for a silicon homojunction bipolar transistor with the same device structure. The effects of the amorphous heteroemitter material parameters (doping, electron drift mobility, defect density and interface state density) on frequency response are then examined to find the requirements for an amorphous heteroemitter material such that the HBT has better frequency response than the equivalent homojunction bipolar transistor, We find that an electron drift mobility of at least 100 cm² V^-1 s^-1 is required in the amorphous heteroemitter and at a heteroemitter drift mobility of 350 cm ² V^-1 s^-1 and heteroemitter doping of 5×10¹⁷ cm^-3, a maximum cutoff frequency of 52 GHz can be expected     

Silicon carbide high-power devices

In recent years, silicon carbide has received increased attention because of its potential for high-power devices. The unique material properties of SiC, high electric breakdown field, high saturated electron drift velocity, and high thermal conductivity are what give this material its tremendous potential in the power device arena. 4H-SiC Schottky barrier diodes (1400 V) with forward current densities over 700 A/cm² at 2 V have been demonstrated. Packaged SITs have produced 57 W of output power at 500 MHz, SiC UMOSFETs (1200 V) are projected to have 15 times the current density of Si IGBTs (1200 V). Submicron gate length 4H-SiC MESFETs have achieved f_max=32 GHz, f_T=14.0 GHz, and power density=2.8 W/mm @ 1.8 GHz. The performances of a wide variety of SiC devices are compared to that of similar Si and GaAs devices and to theoretically expected results     

Double-drift-region ion-implanted millimeter-wave IMPATT diodes

A detailed experimental comparison between double-drift-region (DDR) and single-drift-region (SDR) millimeter-wave avalanche diodes is presented. For 50-GHz CW operation, DDR diodes have given a maximum of 1-W output power compared to 0.53 W for the SDR diodes, while maximum efficiencies of 14.2 percent for the DDR and 10.3 percent for the SDR diodes have been obtained. These results are in agreement with the theory of Scharfetter et al. [1] for DDR IMPATT diodes. Both the DDR and SDR diode measurements were made on room temperature, metal heat sinks. The DDR diodes were shown to operate at significantly lower junction temperatures for the same value of output power, indicating a potential reliability advantage. Ion implantation was used to make the p drift region of the p⁺p-n-n⁺50-GHz DDR devices. Otherwise the fabrication (which includes diffusion and epitaxial technologies) and the microwave measurement methods were identical for both types of diodes. Capacitance measurements were compared with calculations to determine the desired doping concentrations for frequencies from 43 to 110 GHz. Experimental results for the higher frequency millimeter-wave region have been obtained on DDR structures with both p and n drift regions implanted. At 92 GHz an output power of 0.18 W and an efficiency of 7.4 percent have been obtained.     

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.     

The ultimate limits of CCD performance imposed by hot electron effects

It is shown that the ultimate speed of charge transfer in silicon charge coupled devices is limited by impact ionization in the silicon and the saturation of the drift velocity. The charge transfer speed of buried channel devices (BCCDs) decreases linearly with the separation, L, between centers of neighboring gates for L ≤ 10 μM. The decrease of the transfer speed of surface channel devices (SCCDs) is linear only for L ≤ 2 μm but is much faster for L > 2 μm. For L ≤ 2 μm, the ultimate charge transfer times of both SCCDs and BCCDs are about the same, corresponding to clock frequencies in the GHz range. Charge coupled devices made in small-energy gap compound semiconductors are also discussed. In spite of the higher carrier mobility, devices in these materials can not be operated at clock frequency above the KHz-MHz range due to interband impact generation of electron-hole pairs in the high electric field.     

1/4 W continuous-wave Q band Gunn oscillator

C.W. Gunn devices using integral-heatsink techniques have been produced with a power output of more than ? W at 31.5 GHz. Conversion efficiencies of up to 4.6% are reported. A tuning range greater than 8 GHz has been obtained.     

Optimum design of n+-n-n+InP devices in the millimeter-range frequency limitation—RF performances

Systematic simulations of n⁺-n-n⁺InP millimeter-wave transferred-electron devices have been performed in order to define the frequency limitation of the fundamental accumulation transmit mode, as well as the maximum RF performance of these devices. The simulations indicate that the use of n⁺-n-n⁺InP devices yields significant net output powers and efficiencies up to 160 GHz, according to the present state of technology.     

X波段FBAR用AlN薄膜制备研究

采用中频磁控溅射法,在硅基上制备了X波段薄膜体声波谐振器(FBAR)滤波器用AlN压电薄膜。对AlN薄膜进行了分析表征,结果表明,AlN压电薄膜具有良好的(002)面择优取向,摇摆曲线半峰宽为2.21°,膜厚均匀性优于0.5%,薄膜应力为-5.02 MPa,应力可在张应力和压应力间进行调节。将该AlN薄膜制备工艺应用于FBAR器件的制作,研制出X波段FBAR器件,谐振频率为9.09 GHz,插入损耗为-0.38 dB。     

High-efficiency TRAPATT operation in X band

High-efficiency TRAPATT operation in X band has been obtained using a silicon p+?n?n+ structure with an integral-heatsink technology. 35.8% efficiency with 12.3 W output and 15 W at 30.6% efficiency have been obtained in the frequency range 8.4?9.6 GHz. Precise doping-level control has enabled a high degree of reproducibility to be realised from slice to slice, and a well characterised processing technology results in high yields of efficient devices.     

Overlength modes of InP transferred-electron devices

Simulations of overlength modes in InP transferred-electron devices indicate microwave conversion efficiencies greater than 25%. The maximum frequency of operation exceeds 20 GHz. but depends markedly on the nature of the electronic intervalley scattering processes and associated relaxation effects.     

MICROX-an all-silicon technology for monolithic microwaveintegrated circuits

An improved silicon-on-insulator (SOI) approach offers devices and circuits operating to 10 GHz by providing formerly unattainable capabilities in bulk silicon: reduced junction-to-substrate capacitances in FETs and bipolar transistors, inherent electrical isolation between devices, and low-loss microstrip lines. The concept, called MICROX (patent pending), is based on the SIMOX process, but uses very-high-resistivity (typically>10000 Ω-cm) silicon substrates, MICROX NMOS transistors of effective gate length 0.25 μm give a maximum frequency of operation, f_max, of 32 GHz and f_T of 23.6 GHz in large-periphery (4 μm×50 μm) devices with no correction for the parasitic effects of the pads. The measured minimum noise figure is 1.5 dB at 2 GHz with associated gain of 17.5 dB, an improvement over previously reported values for silicon FETs     

Advanced devices and components for the millimeter and submillimeter systems

The purpose of this paper is to discuss key topics related to low-noise mixers, high efficiency multipliers, the use of quasi-optical techniques to reduce circuit losses, and the development of very high-Q devices applicable to the millimeter and submillimeter wavelengths [1]-[5]. In particular, we will describe the development of a highly reliable metalized GaAs Ta-Schottky-barrier diode with native-oxide passivation. The zero-bias cutoff frequency of these diodes is greater than 1000 GHz when measured accurately near 60 GHz with a zero-bias junction capacitance near 0.1 pF. This zero-bias cutoff frequency is approximately twice the value for a comparable nonmetallized device. Using these very high-Q devices, we have achieved RF performance that has advanced prior state of the art. In frequency multipliers, doublers (100-200 GHz), and triplers (100-300 GHz), we have realized conversion efficiencies of 12 and 2 percent, respectively. The CW output power of the doubler was 18 mW and that of the tripler 2 mW. In an image-enhanced mixer at 35 GHz with an IF of 1 GHz, we have realized conversion loss below 3 dB including 0.6-dB circuit losses, and less than 5.9-dB noise figure (SSB) including a 2-dB IF noise-figure contribution.     

Prospects of gallium nitride double drift region mixed tunneling avalanche transit time diodes for operation in F, Y and THz bands

The potential of GaN as a wide band gap semiconductor is explored for application as double drift region mixed tunneling avalanche transit time (MITATT) diodes for operation at 120 GHz, 220 GHz and 0.35 THz using some computer simulation methods developed by our group. The salient features of our results have uncovered some peculiarities of the GaN based MITATT devices. An efficiency of more than 20% right up to a frequency of 0.35 THz (from the GaN MITATT diode) seems highly encouraging but a power output of only 0.76 W is indicative of its dismal fate. The existence of a noise measure minimum at the operating frequency of 0.35 THz is again exhilarating but the value of the minimum is miserably high i.e. more than 33 dB. Thus, although GaN is a wide band gap semiconductor, the disparate carrier velocities prevent its full potential from being exploited for application as MTATT diodes.