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We report, for the first time, the impact of proton irradiation on fourth-generation SiGe heterojunction bipolar transistors (HBTs) having a record peak unity gain cutoff frequency of 350 GHz. The implications of aggressive vertical scaling on the observed proton tolerance is investigated through comparisons of the pre-and post-radiation ac and dc figures-of-merit to observed results from prior SiGe HBT technology nodes irradiated under identical conditions. In addition, transistors of varying breakdown voltage are used to probe the differences in proton tolerance as a function of collector doping. Our findings indicate that SiGe HBTs continue to exhibit impressive total dose tolerance, even at unprecedented levels of vertical profile scaling and frequency response. Negligible total dose degradation in [beta] (0.3%), [[Florin].sub.T] and [[Florin].sub.max] (6%) are observed in the circuit bias regime, suggesting that SiGe HBT BiCMOS technology is potentially a formidable contender for high-performance space-borne applications. Index Terms--Breakdwon voltage, heterojunction bipolar transistors (HBT), proton tolerance, SiGe, silicon-germanium, technology scaling.

The relatively less exploited terahertz band possesses great potential for a variety of important applications, including communication applications that would benefit from the enormous bandwidth within the terahertz spectrum. This paper overviews an approach toward terahertz applications based on SiGe heterojunction bipolar transistor (HBT) technology, focusing on broad-band communication applications. The design, characteristics, and reliability of SiGe HBTs exhibiting record [f.sub.T] of 375 GHz and associated [f.sub.max] of 210 GHz are presented. The impact of device optimization on noise characteristics is described for both low-frequency and broad-band noise. Circuit implementations of SiGe technologies are demonstrated with selected circuit blocks for broad-band communication systems, including a 3.9-ps emitter coupled logic ring oscillator, a 100-GHz frequency divider, 40-GHz voltage-controlled oscillator, and a 70-Gb/s 4:1 multiplexer. With no visible limitation for further enhancement of device speed at hand, the march toward terahertz band with Si-based technology will continue for the foreseeable future. Index Terms--BiCMOS integrated circuits, communication systems, heterojunction bipolar transistors (HBTs), high-speed integrated circuits.

SiGe HBT transistoprs achieving over 200 GHz f[subscript gamma] and f[subscript MAX] are examined and reported.

P-type SiGe temperature-dependent minority electron mobilities have been measured.

A double mesa-structure Si/SiGe heterojunction bipolar transistor (HBT) and novel micromachined lumped passive components have been developed and successfully applied to the fabrication of X- and Ku-band monolithic amplifiers. The fabricated 5 x 5 [[[micro]meter].sup.2] emitter-size Si/SiGe HBT exhibited a dc-current gain [Beta] of 109, and [f.sub.T] and [f.sub.max] of 28 and 52 GHz, respectively. Micromachined spiral inductors demonstrated resonance frequency of 20 GHz up to 4 nil, which is higher than that of conventional spiral inductors by a factor of two. Single-, dual-, and three-stage X-band amplifiers have been designed, based on the extracted active- and passive-device model parameters. A single-stage amplifier exhibited a peak gain of 4.0 dB at 10.0 GHz, while dual- and three-stage versions showed peak gains of 5.7 dB at 10.0 GHz and 12.6 dB at 11.1 GHz, respectively. A Ku-band single-stage amplifier has also been designed and fabricated, showing a peak gain of 1.4 dB at 16.6 GHz. Matching circuits for all these amplifiers were implemented by lumped components, leading to a much smaller chip size compared to those employing distributed components as matching elements. Index Terms - Amplifier, HBT, micromachining, MMIC, resonance frequency, SiGe.

Embedding magnetic layers in inductors is an attractive option for increasing inductance density, which is a critical issue for radiofrequency applications. In this letter, we develop a magnetostatic model for square spiral inductors incorporating a magnetic layer. In our model, we assume that the permeability of the magnetic layer is isotropic and infinite. The model provides a fast and effective numerical calculation of the inductance of inductors incorporating a magnetic layer. We show the derivation of the model and provide calculation results for various inductor structures. Index Terms--inductors, magnetic films, magnetostatics.

A 138 GHz down-conversion mixer with a branch-line coupler has been developed based on a 90 nm CMOS technology. The fabricated mixer shows a differential conversion gain of 3.7 dB with the mixer core drawing a current 0.66 mA from a 1.2 V supply. The 1 dB gain compression point is estimated to be larger than -6 dBm. The mixer occupies 0.61 × 0.62 mm2 of chip area excluding pads. [ABSTRACT FROM AUTHOR]