Cryogenic probe station for on-wafer characterization of electrical devices

A probe station, suitable for the electrical characterization of integrated circuits at cryogenic temperatures is presented. The unique design incorporates all moving components inside the cryostat at room temperature, greatly simplifying the design and allowing automated step and repeat testing. The system can characterize wafers up to 100 mm in diameter, at temperatures <20 K. It is capable of highly repeatable measurements at millimeter-wave frequencies, even though it utilizes a Gifford McMahon cryocooler which typically imposes limits due to vibration. Its capabilities are illustrated by noise temperature and S-parameter measurements on low noise amplifiers for radio astronomy, operating at 75–116 GHz

Coherent polarimeter modules for the QUIET experiment

The Q/U Imaging Experiment (QUIET) is an experimental program to make very sensitive measurements of the Cosmic Background Radiation (CMB) polarization from the ground. A key component of this project is the ability to produce large numbers of detectors in order to achieve the required sensitivity. Using a breakthrough in mm-wave packaging at JPL, a polarimeter-on-a-chip has been developed which lends itself to the mass-production techniques used in the semiconductor industry. We describe the design, implementation and performance of these polarimeter modules for QUIET Phase I and briefly discuss the plans for further module development

Coherent Arrays for Astronomy and Remote Sensing - Final Report

The Coherent Arrays for Astronomy and Remote Sensing Program sponsored by the Keck Institute for Space Studies has had a profound impact on astronomy at Caltech – both at JPL and on campus – and worldwide. It provided funds for the establishment of a world-class coherent detector laboratory – the Cahill Radio Astronomy Laboratory (CRAL) that, in collaboration with JPL and Northrop Grumman, now sets the global standard in coherent detectors in the centimeter-millimeter wavelength range – as shown by three key highlights: (i) NRAO’s recent selection of CRAL MMIC detectors over its own in house MIC detectors for the upgrade of the ALMA Band 2 receivers; (ii) NSF’s funding of a 16-element 85 GHz – 115 GHz focal plane array (ARGUS) for the Green Bank Telescope ($1M); and (iii) NSF’s funding of the 26 GHz – 34 GHz CO Mapping Array Pathfinder (COMAP$2.5M). The funding of COMAP was particularly important since it demonstrated in the wake of the NSF decline of the CARMA proposal (2014) that the US astronomy community and the NSF were prepared to fund large new projects at the Owens Valley Radio Observatory (OVRO), enabling the OVRO to re-establish itself as a world-class radio observatory and convincing Caltech to continue its funding of the OVRO. It is no exaggeration that the KISS coherent detector program played THE major role in saving the OVRO. The position of the CRAL and of the OVRO is now very strong and the staff, decimated by the CARMA decline, is being rebuilt and is once more at a robust strength. Two new multi-national partnerships – the Radio Astronomy Partnership (RAP) and the MMIC Partnership (MMICP) have been established at Caltech as a direct result of the KISS investment in creating the CRAL, and these are providing independent funding to OVRO and the CRAL. There are now eight agency-funded programs at the OVRO and we are optimistic about the prospects of having two more programs funded in the next year, in view of important science breakthroughs at OVRO over the last 6 months

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization

125 - 211 GHz low noise MMIC amplifier design for radio astronomy

To achieve the low noise and wide bandwidth required for millimeter wavelength astronomy applications, superconductor-insulator-superconductor (SIS) mixer based receiver systems have typically been used. This paper investigates the performance of high electron mobility transistor (HEMT) based low noise amplifiers (LNAs) as an alternative approach for systems operating in the 125 — 211 GHz frequency range. A four-stage, common-source, unconditionally stable monolithic microwave integrated circuit (MMIC) design is presented using the state-of-the-art 35 nm indium phosphide HEMT process from Northrop Grumman Corporation. The simulated MMIC achieves noise temperature (T_e) lower than 58 K across the operational bandwidth, with average T_e of 38.8 K (corresponding to less than 5 times the quantum limit (hf/k) at 170 GHz) and forward transmission of 20.5 ± 0.85 dB. Input and output reflection coefficients are better than -6 and -12 dB, respectively, across the desired bandwidth. To the authors knowledge, no LNA currently operates across the entirety of this frequency range. Successful fabrication and implementation of this LNA would challenge the dominance SIS mixers have on sub-THz receivers

A Physical Model for Drain Noise in High Electron Mobility Transistors: Theory and Experiment

We report the on-wafer characterization of $S$-parameters and microwave noise temperature ($T_{50}$) of discrete metamorphic GaAs high electron mobility transistors (HEMTs) at 40 K and 300 K over a range of drain-source voltages ($V_{DS}$). From these data, we extract a small-signal model and the drain noise temperature ($T_{d}$) at each bias and temperature. We find that $T_d$ follows a superlinear trend with $V_{DS}$ at both temperatures. These trends are interpreted by attributing drain noise to a thermal component associated with the channel resistance and a component due to real-space transfer (RST) of electrons from the channel to the barrier [1]. In the present devices at the minimum $T_{50}$, RST contributes $\sim 10$% of the drain noise at cryogenic temperatures. At 300 K, the contribution increases to over $\sim 60$% of the total drain noise. This finding indicates that improving the confinement of electrons in the quantum well could enable room-temperature receivers with up to $\sim 50$% lower noise temperatures by decreasing the contribution of RST to drain noise.Comment: 6 pages, 6 figure

Centimeter-wave continuum radiation from the rho Ophiuchi molecular cloud

The rho Oph molecular cloud is undergoing intermediate-mass star formation. UV radiation from its hottest young stars heats and dissociates exposed layers, but does not ionize hydrogen. Only faint radiation from the Rayleigh-Jeans tail of ~10-100K dust is expected at wavelengths longwards of 3mm. Yet Cosmic Background Imager (CBI) observations reveal that the rho Oph W photo-dissociation region (PDR) is surprisingly bright at centimetre wavelengths. We searched for interpretations consistent with the WMAP radio spectrum, new ISO-LWS parallel mode images and archival Spitzer data. Dust-related emission mechanisms at 1 cm, as proposed by Draine & Lazarian, are a possibility. But a magnetic enhancement of the grain opacity at 1cm is inconsistent with the morphology of the dust column maps Nd and the lack of detected polarization. Spinning dust, or electric-dipole radiation from spinning very small grains (VSGs), comfortably explains the radio spectrum, although not the conspicuous absence from the CBI data of the infrared circumstellar nebulae around the B-type stars S1 and SR~3. Allowing for VSG depletion can marginally reconcile spinning dust with the data. As an alternative interpretation we consider the continuum from residual charges in rho Oph W, where most of carbon should be photoionised by the close binary HD147889 (B2IV, B3IV). Electron densities of ~100 cm^{-3}, or H-nucleus densities n_H > 1E6 cm^{-3}, are required to interpret rho Oph W as the CII Stromgren sphere of HD147889. However the observed steep and positive low-frequency spectral index would then require optically thick emission from an hitherto unobserved ensemble of dense clumps or sheets with a filling factor ~1E-4 and n_H ~ 1E7 cm^{-3}.Comment: accepted for publication in MNRA

Investigation of Cryogenic Current-Voltage Anomalies in SiGe HBTs: Role of Base-Emitter Junction Inhomogeneities

The anomalous current-voltage characteristics of cryogenic SiGe heterojunction bipolar transistors (HBTs) have been a topic of investigation for many years. Proposed explanations include quasiballistic transport of electrons across the base or tunneling from the emitter to the collector, but inconsistencies exist with these hypotheses. Although similar behavior occurs in Schottky junctions and has been attributed to spatial inhomogeneities in the base-emitter junction potential, this explanation has not been considered for SiGe HBTs. Here, we experimentally investigate this hypothesis by characterizing the base-emitter junction ideality factor and built-in potential of a SiGe HBT versus temperature using a cryogenic probe station. The temperature-dependence of the ideality factor and the relation between the built-in potential as measured by capacitance-voltage and current-voltage characteristics are in good qualitative agreement with the predictions of a theory of electrical transport across a junction with a Gaussian distribution of potential barrier heights. These observations support the origin of cryogenic electrical anomalies in SiGe HBTs as arising from lateral inhomogeneities in the base-emitter junction potential. This work helps to identify the physical mechanisms limiting the cryogenic microwave noise performance of SiGe HBTs