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Proton radiation effects in vertical SiGe HBTs fabricated on CMOS-compatible silicon-on-insulator (SOI) are investigated for the first time. Proton irradiation at 63 MeV is found to introduce base leakage current at low base-emitter voltage, delay the onset of Kirk effect at high injection, and increase the frequency response of SiGe HBTs on SOI. The latter two effects are in contrast to those found in conventional bulk SiGe HBTs. Proton irradiation also generates positive fixed oxide and interface charge in the buried oxide, which alters both AI-1 and B[V.sub.CEO] in the SiGe HBT by modulating the electric field in the collector region. Index Terms--HBT, radiation, SiGe, SOI.

A frequency-domain lumped-nonlinear-source behavioral model is presented. This generalized two-port nonlinear model is used to characterize the linearity of either RF devices or circuits. Similar to two-port ac behavioral models (i.e., using S-, Y-, Z-, or H-parameters), this nonlinear model supports combinations such as shunt, series, and cascade, and thus is suitable for systematic analysis. This model is then applied to analyze the impact of harmonic impedance on the second-order intermodulation and third-order intermodulation of a state-ofthe-art SiGe HBTs and circuits. Simple and general linearity expressions are then derived. Harmonic load--pull simulations and measurements are used to demonstrate the usefulness of the proposed analysis technique. Index Terms--Behavioral model, harmonic load--pull, linearity optimization, nonlinear source, Volterra series.

A new four-port scattering parameter (S-parameter) and broad-band noise deembedding methodology is presented. This deembedding technique considers distributed on-wafer parasitics in the millimeter-wave band (f > 30 GHz). The procedure is based on simple analytical calculations and requires no equivalent circuit modeling or electromagnetic simulations. Detailed four-port system analysis and deembedding expressions are derived. Comparisons between this new method and the industry-standard 'open-short' method were made using measured and simulated data on state-of-the-art SiGe HBTs with a maximum cutoff frequency of approximately 180 GHz. The comparison demonstrates that better accuracy is achieved using this new four-port method. Based on a combination of measurements and HP-ADS simulations, we also show that this new technique can be used to accurately extract the S-parameters and broad-band noise characteristics to frequencies above 100 GHz. Index Terms--Deembedding, noise, noise correlation matrix, parasitics, S-parameters, SiGe HBT, Y-parameters.

Field-induced alignment of [O.sub.2] and [H.sub.2] was experimentally studied with varying laser intensities of below ionization threshold and beyond ionization threshold. The results indicated that alignment and ionization coexisted for laser pulses with tens of femtoseconds duration and therefore, the degree of alignment should be taken into account when qualitatively comparing the ion yields of these molecules with their companion atoms.

Two-tone intermodulation in ultrahigh vacuum/chemical vapor deposition SiGe heterojunction bipolar transistors (HBTs) were analyzed using a Volterra-series-based approach that completely distinguishes individual nonlinearities. Avalanche multiplication and collector-base (CB) capacitance were shown to be the dominant nonlinearities in a single-stage common-emitter amplifier. At a given [I.sub.C], an optimum [V.sub.CE] exists for a maximum third-order intercept point (IIP3). The IIP3 is limited by the avalanche multiplication nonlinearity at low [I.sub.C], and limited by the [C.sub.CB] nonlinearity at high [I.sub.C]. The decrease of the avalanche multiplication rate at high [I.sub.C] is beneficial to linearity in SiGe HBTs. The IIP3 is sensitive to the biasing condition because of strong dependence of the avalanche multiplication current and CB capacitance on [I.sub.C] and [V.sub.CE]. The load dependence of linearity was attributed to the feedback through the CB capacitance and the avalanche multiplication in the CB junction. Implications on the optimization of the transistor biasing condition and transistor structure for improved linearity are also discussed. Index Terms--Avalanche multiplication, linearity, nonlinearity cancellation, RF technology, SiGe HBT, Volterra series.