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1,352 results on '"Cressler, John D."'

1. Probing the Magnetodynamics of Magnetic Tunnel Junctions with the Aid of SiGe HBTs

Author

Dark, Jason, Ying, Hanbin, Nunn, Grant, Cressler, John D., and Davidovic, Dragomir

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

High impedance (about 1 Megaohm) magnetic tunnel junctions (MTJs) are used to observe and record the magnetodynamics of the nanomagnets that form the junctions themselves. To counteract the bandwidth limitations caused by the high impedance of the junction and the parasitic capacitance intrinsic to any cryogenic system, silicon-germanium heterojunction bipolar transistors (SiGe HBTs) are used as cryogenic preamplifiers for the MTJs. The resulting measurement improvements include an increase in bandwidth by a factor of 3.89, an increase in signal-to-noise ratio by a factor of 6.62, and a gain of 7.75 of the TMR signal produced by the MTJ. The limitation to the measurement system was found to be from the external, room temperature electronics. Despite this limitation, these improvements allow for better time-resolved magnetodynamics measurements of the MTJs. These experiments pave the way for future cryogenic, magnetodynamics measurement improvements, and could even be useful in cryogenic memory applications., Comment: 9 pages, 8 figures

Published
2018

6. TID Testing of SiGe Microelectronics Using High-Flux 1-MeV Electrons for Europa-Surface Missions

Author

Brumbach, Zachary R., primary, Teng, Jeffrey W., additional, Nergui, Delgermaa, additional, Heimerl, Justin P., additional, Ringel, Brett L., additional, Mensah, Yaw A., additional, Sam, Delwyn G., additional, Moody, Jackson P., additional, Blalock, Benjamin J., additional, Thorburn, Dennis O., additional, Del Castillo, Linda, additional, Mojarradi, Mohammad M., additional, and Cressler, John D., additional

Published
2024
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12. FIPSER: Performance Study of a Readout Concept With Few Digitization Levels for Fast Signals

Author

Limyansky, Brent, Reese, Robert, Cressler, John D., Otte, Adam Nepomuk, Taboada, Ignacio, and Ulusoy, Cagri

Subjects
Physics - Instrumentation and Detectors
Abstract

We discuss the performance of a readout system, Fixed Pulse Shape Efficient Readout (FIPSER), to digitize signals from detectors with a fixed pulse shape. In this study we are mainly interested in the readout of fast photon detectors like photomultipliers or Silicon photomultipliers. But the concept can be equally applied to the digitization of other detector signals. FIPSER is based on the flash analog to digital converter (FADC) concept, but has the potential to lower costs and power consumption by using an order of magnitude fewer discrete voltage levels. Performance is bolstered by combining the discretized signal with the knowledge of the underlying pulse shape. Simulated FIPSER data was reconstructed with two independent methods. One using a maximum likelihood method and the other using a modified chisquared test. Both methods show that utilizing 12 discrete voltage levels with a sampling rate of 4 samples per full width half maximum (FWHM) of the pulse achieves an amplitude resolution that is better than the Poisson limit for photon-counting experiments. The time resolution achieved in this configuration ranges between 0.02 - 0.16 FWHM and depends on the pulse amplitude. In a situation where the waveform is composed of two consecutive pulses the pulses can be separated if they are at least 0.05 - 0.30 FWHM apart with an amplitude resolution that is better than 20%., Comment: 23 pages, 11 figures

Published
2016
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17. Record Maximum Oscillation Frequency in C-face Epitaxial Graphene Transistors

Author

Guo, Zelei, Dong, Rui, Chakraborty, Partha Sarathi, Lourenco, Nelson, Palmer, James, Hu, Yike, Ruan, Ming, Hankinson, John, Kunc, Jan, Cressler, John D., Berger, Claire, and de Heer, Walt A.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The maximum oscillation frequency (fmax) quantifies the practical upper bound for useful circuit operation. We report here an fmax of 70 GHz in transistors using epitaxial graphene grown on the C-face of SiC. This is a significant improvement over Si-face epitaxial graphene used in the prior high frequency transistor studies, exemplifying the superior electronics potential of C-face epitaxial graphene. Careful transistor design using a high {\kappa} dielectric T-gate and self-aligned contacts, further contributed to the record-breaking fmax.

Published
2013
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23. Cryogenic Total-Ionizing-Dose Response of 4th-Generation SiGe HBTs Using 1-MeV Electrons for Europa-Surface Applications

Author

Teng, Jeffrey W., primary, Nergui, Delgermaa, additional, Tzintzarov, George N., additional, Ringel, Brett L., additional, Brumbach, Zachary R., additional, Heimerl, Justin P., additional, Mensah, Yaw A., additional, Moody, Jackson P., additional, Thorbourn, Dennis O., additional, Castillo, Linda Del, additional, Mojarradi, Mohammad M., additional, Blalock, Benjamin J., additional, and Cressler, John D., additional

Published
2023
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26. SET-Induced Dropout and Recovery of Cross-Coupled and Differential-Colpitts Microwave Oscillators Using SiGe HBTs

Author

Teng, Jeffrey W., Mensah, Yaw A., Brumbach, Zachary R., Ildefonso, Adrian, Khachatrian, Ani, McMorrow, Dale, and Cressler, John D.

Abstract

Radio frequency (RF) communications systems in space flight are subject to single-event upsets (SEUs) due to dropout of the local oscillator (LO) during a single-event transient (SET), named here as single-event dropout (SEDO). If the duration of the SEDO is substantial, it inevitably compromises data. To help alleviate SEUs due to SEDO, the present work compares the dropout dynamics and recovery times of two types of RF $\boldsymbol {LC}$ oscillators with matched performance: the cross-coupled and the differential-Colpitts. The SEDO responses of both oscillators were tested using a pulsed laser to deposit charge via a two-photon absorption (TPA) process. For matched electrical performance and laser excitation conditions, the Colpitts oscillator demonstrated $14\times $ faster recovery. This improved response was examined using a hybridized circuit/technology computer-aided design (TCAD) simulation approach, and it was determined that a lower impedance at the bases of critical oscillating transistors naturally reduces the SEDO sensitivity for Colpitts oscillators. While cross-coupled oscillators are widely used, the present work demonstrates that Colpitts oscillators should instead be considered in frequency synthesizers to mitigate SEUs due to SEDO in oscillators.

Published
2024
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27. Comparing Digital Modulation Schemes in RF Receivers for Bit Errors Induced by Single-Event Transients in the Low-Noise Amplifier

Author

Nergui, Delgermaa, Teng, Jeffrey W., Brumbach, Zachary R., Ildefonso, Adrian, Rao, Sunil G., Khachatrian, Ani, McMorrow, Dale, and Cressler, John D.

Abstract

Standard digital modulation schemes are compared for receiver-level single-event upset (SEU) sensitivity. Single-event transients (SETs) on the wideband silicon–germanium (SiGe) low-noise amplifier (LNA) carrying on–off keying (OOK), binary phase-shift keying (BPSK), and frequency-shift keying (2-FSK) modulated data were induced using laser pulses. Both the modulation scheme and its detection method had a significant impact on the SEU sensitivity of the receiver. The SET sensitivity and noise sensitivity of the modulation schemes and demodulation techniques were correlated. Therefore, designing a receiver to be more robust to noise inherently makes it more robust to SETs. For space missions that anticipate a high flux of radiation, taking SETs into account when choosing the radio frequency (RF) modulation scheme and the demodulation method may be important to avoid underestimating the total bit-error rate (BER) when other system trade-offs are compared against the system BER.

Published
2024
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28. Effects of Collector Profile on the SET Response of 130-nm High-Speed and High-Breakdown SiGe HBTs

Author

Brumbach, Zachary R., Nergui, Delgermaa, Teng, Jeffrey W., Mensah, Yaw A., Sam, Delwyn G., Ildefonso, Adrian, Khachatrian, Ani, McMorrow, Dale, and Cressler, John D.

Abstract

A comparison of laser-induced single-event transients (SETs) in silicon-germanium heterojunction bipolar transistor (SiGe HBT) variants designed for high-speed (HS) applications and high-breakdown (HB) applications is presented. A significantly lower amplitude SET response at low laser pulse energies was observed in the HS device compared to the HB device. At high laser pulse energies, however, the transient amplitudes converged and produced a nearly identical response. A 3-D technology computer-aided design (TCAD) model of a SiGe HBT was used to understand the differences between the observed SET responses. During an SET produced by a low laser pulse energy, the mean electric field in the collector-base (CB) junction of a simulated HB device is shown to have a greater magnitude across the depletion region compared to that of its HS counterpart. Motivated by the proportional relationship between drift current and CB junction electric field, a greater breakdown voltage device produced a larger SET response. During an SET produced by a high laser pulse energy, the charge from the SET exceeded the collector doping in both the HS and HB SiGe HBT. This creates a conductive path to the output terminal, removing the dependence of collector doping on SET amplitude. The results of this study should help inform design choices of which device breakdown variant should be used in a given circuit if SETs are a major consideration for the application.

Published
2024
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