A 45 nm CMOS miniature phase shifter with constant amplitude response

We present analysis, optimization, design and characterization of an integrated passive analog phase shifter at 24 GHz in a commercially available 45 nm RF-CMOS process. The design is based on a well-known RC bridge topology, which was optimized for maximum phase shift and minimal amplitude response variation versus phase and frequency. Phase is controlled by varying DC voltage on a varactor, resulting in 60° maximum phase shift with 0.1 dB amplitude variation at 24 GHz. The size of the phase shifter circuit excluding pads and input/output buffers is 40×50 μm².     

Characterization of dark noise in CdZnTe spectrometers

Systematic measurements of dark noise spectra of CdZnTe x- and γ-ray spectrometers, correlated with the dc I-V characteristics and detector technology, are reported. The dark noise of two innovative CdZnTe spectrometer configurations are studied: metal-semiconductor-metal (MSM) resistive detectors with three terminals as well as heterostructure PIN detectors with thermally evaporated n⁺ CdS and p⁺ ZnTe contacts, which are fabricated on high pressure Bridgman CdZnTe (Zn=10%) crystals. The two innovative CdZnTe spectrometer configurations presented here exhibit very low dark (leakage) current. By reducing the dc value of the dark (leakage) current below 1 nA, shot noise becomes the dominant noise mechanism and the contribution of 1/f noise becomes negligible. The use of non-injecting contacts (evaporated gold) for the MSM detectors and the operation of the PIN detector in the reverse bias mode prevent generation-recombination noise which becomes dominant with injecting contacts (for example MSM detectors with evaporated indium and titanium contacts) or when operating the PIN detector in the forward bias mode. Surface leakage is reduced by applying surface passivation but is eliminated only by using the three terminal MSM configuration which exhibits simple shot noise instead of the suppressed shot noise observed in the two terminal MSM spectrometers. The noise measurements are useful for optimizing detector technology.     

Dark noise currents and energy resolution of CdZnTe spectrometers

The effect on energy resolution of dark noise currents experimentally observed in state of the art CdZnTe spectrometers is quantitatively analyzed. Expressions for the energy resolution determined by shot noise, generation-recombination noise, and 1/f noise are discussed in turn and are compared with the linewidth due to incomplete charge collection. The effect of the dark noise upon energy resolution is directly measured by monitoring the broadening of peaks provided by a pulser, due to biased, non-irradiated CdZnTe spectrometers that are connected in parallel. The noise characteristics of the spectrometers under study were measured separately and their dominant noise mechanism is characterized. In this manner, the effect on resolution of the dark noise is correlated not only with the dc value of the dark current but also with the noise spectral behavior which is determined by the noise mechanism.     

Surface passivation of backside-illuminated indium antimonide focalplane array

A novel surface passivation tailored to a two-dimensional array of small-area, gate-controlled InSb photovoltaic diodes fabricated on etch-thinned bulk InSb wafers, with backside illumination, is presented. The surface passivation is based on a controlled surface treatment that reduces the native oxide and is followed by photon-assisted deposition of SiO_x. Thinned bulk n-type InSb with (111) orientation forms two distinctive types of interface on the In and Sb faces, respectively. The In face forms an accumulated interface with reduced surface recombination velocity. The Sb face forms a slightly accumulated interface, with a relatively small concentration of fast and slow surface states. The current-voltage and differential resistance-voltage characteristics of implanted p⁺-n photodiodes exhibit nearly flat behavior up to 1-V reverse bias with reduced leakage currents. The R_o×A product of small-geometry diodes is 5×10⁴ Ω-cm² at 77 K     

Growth and properties of Hg1-x Cdx Te epitaxial layers

The growth of epitaxial layers of mercury-cadmium-telluride (Hg_1-xCd_xTe) with relatively low x (0.2-0.3) from Te-rich solutions in an open tube sliding system is studied. The development of a semiclosed slider system with unique features permits the growth of low x material at atmospheric pressure. The quality of the films is improved by the use of Cd_1-yZ_yTe and Hg_1-xCd_xTe substrates instead of CdTe. The substrate effects and the growth procedure are discussed and a solidus line at a relatively low temperature is reported. The asgrown epitaxial layers are p-type with hole concentration of the order of 1·10¹⁷ cm⁻³, hole mobility of about 300 cm²·V⁻¹ sec⁻¹ and excess minority carrier life-time of 3 nsec, at 77 K.     

Ion-sensitive field-effect transistors in standard CMOS fabricated by post processing

Highly integrated ion-sensitive field-effect transistor (ISFET) microsystems require the monolithic implementation of ISFETs, CMOS electronics, and additional sensors on the same chip. This paper presents new ISFETs in standard CMOS, fabricated by post-processing of a standard CMOS VLSI chip. Unlike CMOS compatible ISFETs fabricated in a dedicated process, the new sensors are directly combined with state-of-the-art CMOS electronics and are subject to continuous technology upgrading. The ISFETs presented include an intermediate gate formed by one or more conducting layers placed between the gate oxide and the sensing layer. The combination of the highly isolating gate oxide of the MOS with a leaky or conducting sensing layer allows the use of low temperature materials that do not damage the CMOS chip. The operation of ISFETs with an intermediate gate and sensing layers fabricated at low temperature is modeled. ISFETs with a linear pH response and drift as low as 0.3 mV/h are reported.     

Media Fabric — A Process-Oriented Approach to Media Creation and Exchange

This paper explores the emergence of a new paradigm we call the 'media fabric' — a semi-intelligent organism consisting of a vast and evolving collection of media artefacts, structures and programs that support our engagement in meaningful real-time dialogues, art making, and social interaction. Situated in and around modern communications networks, the media fabric beckons us into an evolving landscape of creative story potential that is synergistic with our imagination, integral to our everyday life, mindful of itself and our intentions, improvisationally shaped, and provides us with interactions and remaindered artefacts that are evocative and self-reflective.     

Measurement of differential capacitance in solutions of low conductivity

An experimental set-up for measuring the differential capacitance at the dme for cell resistances up to several M is described. The system performance is analysed and experimental differential capacitance vs potential curves at the interface between the dme and 10⁻³, 10⁻⁴, 10⁻⁵ M NaF are presented. The method involves the measurement of the charging current when a linear sweep is supplied to the cell, utilizing positive feedback for the compensation of the cell resistance. Positive feedback for compensation is found to be especially useful for equilibrium capacitance measurements since it accelerates the attainment of equilibrium. Instrumental errors and the relation between the accuracy of the capacitance measurement and the error in compensation are discussed. The experimental results for 10⁻³, 10⁻⁴, 10⁻⁵ M NaF are compared with values expected on the basis of Grahame's data for higher concentrations. Agreement is found between experimental and calculated capacitances in the region of zero charge. In the negative polarization region experimental capacitances are lower than calculated capacitances and decrease progressively with decreasing concentrations.