Design and Simulation of Near-Terahertz GaN Photoconductive Switches–Operation in the Negative Differential Mobility Regime and Pulse Compression

Rakheja, Shaloo; Li, Kexin; Dowling, Karen M.; Conway, A. M.; Voss, Lars F.

doi:10.1109/jeds.2021.3077761

Cited by 11 publications

(2 citation statements)

References 32 publications

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“…However, these devices did not use the C-doped layer that is central to the present high-speed operation. However, progress on the device fabrication side is being made [53,54]. Hence, it is likely that a true high-speed pulse compression GaN PCSS may be realized in the near future that is capable of operating in the 100 GHz regime as predicted here for a rugged and robust advanced high power PCSS alternative.…”

Section: Discussionmentioning

confidence: 89%

Density-Dependent Effects on Pulse Compression in GaN Photodetectors Probed by Monte Carlo Studies

2022

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With increases in the demand for faster electronic switching, requirements for higher operating voltages and currents, and the need to perform under harsh environments while operating at even higher frequencies, the research focus in photoconductive semiconductor switch (PCSS) technology has shifted to wide bandgap semiconductors. Here, we examine the possibility of pulse compression in carbon-doped PCSS devices based on the negative differential mobility concept for faster operation. Monte Carlo simulations are used to build in and model various effects on electron transport including degeneracy, charge polarization, and scattering within a three-valley model fitted to bandstructure calculations. The focus is on exploring the density dependence of pulse compression. Thresholds for the biasing fields naturally emerge. Predictive analysis of the output full-width half-maximum (FWHM) current waveforms, as well as the dynamics of the internal charge cloud behavior, and occupancy of the various valleys within GaN are all obtained. Our results show that an increase in carrier density can increase pulse compression and create pulse-widths that are smaller than the FWHM of the input optical excitation. This bodes well for enhanced repetition rates. Variations produced by moving the laser spot along the GaN PCSS length are also examined. Though data for GaN are not yet available, the trends compare well qualitatively with previous reports for GaAs.

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Section: Discussionmentioning

confidence: 89%

Density-Dependent Effects on Pulse Compression in GaN Photodetectors Probed by Monte Carlo Studies

2022

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“…owadays, with the development of GaN-based optoelectronic devices, their applications could be widely expanded, such as photoconductive semiconductor switches (PCSSs). PCSSs are able to withstand both high voltage and high current with sub-nanosecond rise times, 1) and hence could be used in dielectric wall accelerators, 2) THz radiation sources, 3) impulse radar, 4) and so on. Most of the previous PCSS devices are fabricated on Si or GaAs substrates.…”

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confidence: 99%

Investigation on the thermal stability of reflective and anti-reflective coatings on freestanding GaN

Sun¹,

Wang²,

Hu³

et al. 2023

Appl. Phys. Express

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The reflective (RC) and anti-reflective coatings (ARC) on freestanding GaN were fabricated using a stack of TiO2/SiO2 multi-layers, which changes the reflectance at 532 nm from 17.0% to 2.5% and 99.6% respectively and proves the effectiveness of RC and ARC. The reflection spectra of annealed RC and ARC both show a blueshift of about 52 nm after high temperature annealing, because of the phase transition of TiO2 from amorphism to anatase at high temperature. In order to improve the thermal stability of RC and ARC, we could increase the thickness of TiO2 and SiO2 proportionally during the coating process.

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Design considerations for gallium arsenide pulse compression photoconductive switch

Dong

Dowling

Hau‐Riege

et al. 2022

Journal of Applied Physics

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In this paper, we present the physics and design-space exploration of a novel pulse compression photoconductive switch (PCPS) using semi-insulating gallium arsenide (GaAs) operating in the negative differential mobility (NDM) regime of electron transport. We systematically quantify the relationship between the PCPS performance and various design options, including contact separation, laser energy and placement, and trap dynamics. Specifically, we report the full-width at half-maximum and the peak output current generated by the PCPS as a function of applied electrical and optical bias. We discuss the optimal spacing between the electrodes and the distance of the laser spot to the anode to achieve higher electron confinement and superior radio-frequency (RF) metrics. Reducing the laser energy is important to prevent the appearance of secondary peaks due to diffusive transport, but there exists a trade-off between the bandwidth and the maximum current of the PCPS. We also compare the PCPS response with and without trap dynamics and find that the electrostatic screening from the trap-induced space charge is time-independent when the trapping time constant is set larger than the recombination lifetime. Overall, trap dynamics are detrimental to performance, unless the compensation doping scheme to achieve semi-insulating GaAs is carefully selected. Results presented in this paper can be used by experimentalists to fine-tune the PCPS design parameters to meet the specifications of various RF applications. Moreover, our results will provide a strong theoretical basis to the measurements of PCPS devices using GaAs and other NDM materials under investigation.

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Design and Simulation of Near-Terahertz GaN Photoconductive Switches–Operation in the Negative Differential Mobility Regime and Pulse Compression

Cited by 11 publications

References 32 publications

Density-Dependent Effects on Pulse Compression in GaN Photodetectors Probed by Monte Carlo Studies

Density-Dependent Effects on Pulse Compression in GaN Photodetectors Probed by Monte Carlo Studies

Investigation on the thermal stability of reflective and anti-reflective coatings on freestanding GaN

Design considerations for gallium arsenide pulse compression photoconductive switch

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