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6CCVD Research

Computationally assessing diamond as an ultrafast pulse shaper for high-power ultrawideband radar

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2023-08-24
JournalFrontiers in Carbon
AuthorsChristopher S. Herrmann, Joseph Croman, Sergey V. Baryshev
InstitutionsUnited States Naval Research Laboratory, Michigan State University
Citations1
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study computationally assesses the use of diamond in Diode Avalanche Shapers (DAS) for generating ultra-fast, high-power pulses critical for Ultrawideband (UWB) radar.

  • Core Achievement: Simulation demonstrated that a diamond DAS significantly outperforms silicon (Si) DAS, achieving a peak output voltage rate of 1 kV/ps.
  • Performance Gain: Diamond DAS provided a 3 to 10-fold increase in output voltage rate compared to Si DAS, resulting in a 10-fold increase in output peak power for the same switching time.
  • Ultrafast Switching: The diamond DAS achieved an ultimate switching time (FWHM) of 5 ps, enabling the generation of MW-scale pulses suitable for 30 GHz UWB radar applications.
  • Material Advantage: Superior performance is attributed to diamond’s high breakdown field (10 MV/cm) and high saturated drift velocity (2 x 107 cm/s), resulting in a Johnson’s Figure of Merit (JFOM) of 200 V/ps (compared to 2 V/ps for Si).
  • Mechanism: The ultrafast switching relies on the streamer mechanism, where the plasma front velocity (vp) in diamond is estimated to be near or above 108 cm/s, overcoming conventional carrier transit time limitations.
  • Device Structure: The simulations focused on a thin-base p-i-n diode structure (10 ”m i-layer) operating under high overvoltage conditions (3 kV input pulse applied to a 1 kV breakdown device).

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Diamond Breakdown Field (Ebr)10MV/cmUltimate material property
Diamond Saturated Drift Velocity (vs)2 x 107cm/sUltimate material property
Diamond Johnson’s Figure of Merit (JFOM)200V/psUltimate differential voltage rate (Ebr x vs)
Si Johnson’s Figure of Merit (JFOM)2V/psUltimate differential voltage rate (Ebr x vs)
Simulated Diamond DAS Peak Output Rate (dV/dt)1kV/psAchieved at 0.1 kV/ps input rate
Simulated Diamond DAS Switching Time (FWHM)5ps10 ”m i-layer structure
Simulated Diamond DAS Output Peak Power0.5MWEstimated for 5 ps pulse
Simulated Input Pulse Peak Voltage3kVGenerated by hypothetical DSRD
Simulated Input Pulse Rise Time1.5nsLinear rise time
Target UWB Frequency30GHzRequires ~10 ps pulse duration
Diode Structurep-i-nN/ASimulated device type (DAS)
i-layer Thickness (Diamond/Thin Si)10”mBase layer thickness
Simulation Temperature300KConstant temperature assumption

Key Methodologies

Section titled “Key Methodologies”

The physical behavior of the Diode Avalanche Shaper (DAS) was modeled using Technology Computer-Aided Design (TCAD) software in a mixed-mode environment, combining device physics and circuit simulation (SPICE-like analysis).

  1. Simulation Platform: Synopsys Sentaurus TCAD was utilized for three-dimensional (3D) device modeling.
  2. Physical Model: The drift-diffusion approach was employed, incorporating constant carrier mobility and carrier velocity saturation at high fields.
  3. Avalanche Dynamics: The Van Overstraeten de-Man model was used to simulate impact ionization and avalanche dynamics. Tunneling-assisted ionization was excluded.
  4. Material Implementation: Diamond was implemented as a custom material using ionization coefficient (α(E)) data based on Watanabe et al. (2001), assuming Ebr ~ 106 V/cm.
  5. Circuit Configuration: The DAS was simulated within a virtual circuit (red box in Figure 1) consisting of a voltage source (hypothetical DSRD input), a DC pre-bias (Vref = 10 V), and a 50 Ω load resistor (RL).
  6. Input Pulse Generation: The input voltage source ramped linearly at rates ranging from 1 V/ps to 100 V/ps to test the sharpening capability.
  7. Benchmarking: The Si DAS model was validated against prior results from Focia et al. (1996) to ensure computational accuracy before simulating the diamond device.

Commercial Applications

Section titled “Commercial Applications”

The development of ultra-fast, high-power diamond switching devices is critical for advancing several high-technology sectors:

  • Ultrawideband (UWB) Radar:
    • Enabling next-generation vehicular radar operating at 30 GHz, requiring 10 ps pulses for high resolution.
    • Achieving cm-range resolution over kilometer distances due to high peak power (MW scale) and short pulse duration.
  • High-Power Pulsed Systems:
    • Serving as compact, lightweight sources for Intentional Electromagnetic Interference (IEMI).
    • Used in high-power accelerator systems and pulsed power generators.
  • Advanced Electronics and Optics:
    • Ultrafast electro-optics and laser technologies requiring sub-10 ps electronic drivers.
    • Discharge/plasma-assisted combustion and chemistry applications.
  • Solid-State Switching:
    • Developing high-power closing switches (DAS) and opening switches (DSRD) with significantly reduced footprint and cooling requirements compared to stacked Si devices.
View Original Abstract

Diamond holds promise to reshape ultrafast and high-power electronics. One such solid-state device is the diode avalanche shaper (DAS), which functions as an ultrafast closing switch where closing is caused by the formation of the streamer traversing the diode much faster than 10 7 cm/s. One of the most prominent applications of DAS devices is in ultrawideband (UWB) radio/radar. Here, we simulate a diamond-based DAS and compare the results to a silicon-based DAS. All DASs were simulated in mixed mode as ideal devices using the drift-diffusion model. The simulations show that a diamond DAS promises to outperform an Si DAS when sharpening the kV nanosecond input pulse. The breakdown field and streamer velocity (∌10 times larger in diamond than Si) are likely to be the major reasons enabling kV sub-50 ps switching using a diamond DAS.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - A study of 4h-SiC diode avalanche shaper [Crossref]
  2. 1970 - Avalanche shock fronts in p-n junctions [Crossref]
  3. 2013 - Safety aspects of people exposed to ultra wideband radar fields [Crossref]
  4. 2011 - Note: picosecond impulse generator driven by cascaded step recovery diode pulse shaping circuit [Crossref]
  5. 1996 - New approaches for designing high voltage, high current silicon step recovery diodes for pulse sharpening applications [Crossref]
  6. 2006 - Ultrashort laser pulse phenomena
  7. 1997 - Powerful semiconductor 80 kv nanosecond pulser [Crossref]
  8. 2017 - Radar services in the 76-81 ghz band report and order - et docket no 15-26
  9. 1997 - Silicon diodes in avalanche pulse-sharpening applications [Crossref]
  10. 1996 - Simple techniques for the generation of high peak power pulses with nanosecond and subnanosecond rise times [Crossref]

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