Udo Lieneweg

Modeling of planar varactor frequency multiplier devices with blocking barriers

Models for optimization of planar frequency triplers with symmetrical C-V curves are presented. The roles and and limitations of various blocking barriers (oxide, Mott, heterojunction) are discussed. Devices with undoped drift regions (BIN) gave moderate efficiency but a broad range of power generation, whereas the devices with doped drift regions (BNN) have high efficiency in a narrower power window. In particular, an upper power limit of the BNN is caused by electron velocity saturation. Implementations in SiO/sub 2/-Si and AlAs-GaAs and means for increasing the power of BNN structures are considered. >

Frequency response of charge transfer in MOS inversion layers

The dynamics of charge transfer from a reservoir into an MOS inversion layer, which limits the frequency response of an MOS transistor or a charge-coupled device, is investigated. Using Berman and Kerrs model of space-charge capacitance in the semiconductor, a small-signal distributed model is developed for an MOS structure which transfers charge in an inversion channel due to a variation in the gate voltage. The dynamics of the charge transfer is characterized by a time constant which is determined by the length of the inversion channel and its mobility. Experimental data of gate capacitance vs frequency, taken from a test structure with a diffused source/drain well, are satisfactorily fitted by theoretical curves derived from the model. The channel mobility is precisely determined from the adjusted time constant. The influence of interface states on the capacitance-frequency relationship is also briefly discussed.

Space-charge behavior of “Thin-MOS” diodes with MBE-grown silicon films

Abstract We present basic theoretical and experimental characteristics of a novel “Thin-MOS” technology, which has promising aspects for integrated high-frequency devices up to several hundred gigahertz. The operation of such devices depends on charge injection into undoped silicon layers of ∼ 1000-A thickness, grown by molecular beam epitaxy on heavily doped substrates, and isolation by thermally grown oxides of ∼ 100-A thickness. Capacitance-voltage characteristics measured at “high” and “low” frequencies agree well with theoretical ones derived from uni- and ambipolar space-charge models. We conclude that after oxidation the residual doping in the epilayer is less than ∼ 10 16 cm −3 and rises by 3 orders of magnitude at the substrate interface within less than 100 A and that interface states at the oxide interface can be kept low.

Measurement and modeling of size and proximity effects in conductor linewidths

The widths of refractory metal, gold, and Permalloy lines were measured as a function of design width W/sub i/ and design spacing S/sub j/ using an electrical test structure, the cross-quad-bridge resistor. The data were characterised by the following: a constant linewidth aberration /spl Delta/W; a characteristic size effect width W/sub c/; and a characteristic proximity effect spacing S/sub c/. With both characteristic dimensions around |/sub c/|/spl ap/|S/sub c/|/spl ap/0.4 /spl mu/m, the effects on a design with W/sub 1spl ap/S/sub 1spl ap/1.2 /spl mu/m are about (W/sub cW/sub 1/)/sup 2spl ap/10% each.<<ETX>>

Extracting contact misalignment from 4- and 6-terminal contact resistors

A heuristic model is derived from simulations describing quantitatively the effect of contact misalignment on four- and six-terminal contact resistance measurements with L-type test structures. The four-terminal resistor pair allows only the extraction of the sum of the misalignment components and the extraction of the average interfacial resistance of the two contacts while a quantitative evaluation is restricted to such small misalignments that the second-order effect can be neglected. The six-terminal contact resistor allows the separation of the misalignment components and the determination of a single interfacial resistance while the magnitude of the misalignment can extend into the validity range of the second-order model.<<ETX>>

Flange correction to four-terminal contact resistance measurements

A heuristic model for flange correction to four-terminal measurements of the interfacial resistance in square contacts between a semiconducting and a metal layer, or between metal layers is presented. The model reproduces results from experiments with geometric variations when a constant interfacial resistivity is fitted, and compares well to simulations.<<ETX>>

Monolithic watt-level millimeter-wave diode-grid frequency tripler array

Thousands of solid-state diodes are monolithically integrated by a metal grid as a highly efficient frequency multiplier which promises watt-level CW output power throughout the millimeter and submillimeter wave region. Different devices such as GaAs Schottky diode, thin MOS diode, and GaAs Barrier-Intrinsic-N+ diode are employed in this study. The approach also results in low-cost fabication and small-size realization.

Comments, with reply, on "Modeling of planar varactor frequency multiplier devices with blocking barriers" by U. Lieneweg et al

The commenter reports that he has conducted a series of measurements for determining the effective series resistance, capacitance, and RC time constant of the back-to-back connected diodes, which exhibit behavior of the effective series resistance and capacitance that is somewhat different than assumed in the commenters thesis (UCLA, 1991) or published in the above-titled paper by V. Lieneweg et al. (ibid., vol.40, no.5, p.839-45, May 1992). These results are presented and discussed. In their reply, Lieneweg et al. take issue with some of the commenters points and defend their results. >

Projected noise in submillimeter-wave mixers with InSb Schottky diodes

The reduction of the equivalent noise temperature in liquidnitrogen-cooled submillimeter-wave mixers by the use of Schottky barriers on InSb instead of GaAs is evaluated by an analytical model that assumes limited local oscillator power and matched impedances. The calculations, executed at 1.0 and 1.8 Thz, take plasma resonance and skin effect into account. For single and multiple contacts on homogeneous semiconductor materials of optimum doping, the noise of InSb diodes is smaller than that of GaAs diodes by a factor of 3 to 14. A simplified model is used to predict the performance of epitaxial structures as well as alternative materials.