Abstract
High purity semi-insulating (HPSI) 4H-silicon carbide (SiC) was used to fabricate lateral and vertical photoconductive semiconductor switches (PCSSs). The lateral PCSSs were illuminated from the frontside (fPCSS) or the backside (bPCSS). The side-illuminated vertical PCSS (vPCSS) was designed to increase the light-matter interaction volume. A 532-nm pulsed laser with adjustable energy was utilized to excite the PCSSs. The turn-on time was found to be highly dependent on the optical illumination energy, and the full-width at half-maximum of the PCSSs output waveforms was related to the peak output voltage. The output electrical pulse from the vPCSS exhibited a shorter turn-on time and a larger pulsewidth than the two types of lateral PCSSs. The vPCSS outperformed the fPCSS and bPCSS in terms of minimum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm{\scriptscriptstyle ON}$ </tex-math></inline-formula> -state resistance and output pulse amplitude under the same optical illumination energy. The vPCSS, which utilizes a large effective contact area to collect photogenerated carriers, also had higher photon absorption efficiency by arranging the optical path at a right angle to the carrier transport. The vPCSS exhibited a minimum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm{\scriptscriptstyle ON}$ </tex-math></inline-formula> -state resistance of 0.34 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> at optical illumination energy of 8 mJ.
Highlights
P HOTOCONDUCTIVE semiconductor switches (PCSSs) have been investigated as promising optoelectronic devices for pulsed power systems since the late 1970s [1]
The conductivity of photoconductive semiconductor switches (PCSSs) operating in the linear mode is proportional to the incident optical power, while the avalanche process dominates in the nonlinear mode, which is called the high gain mode [6], [7]
Several semiconductor materials have been considered as candidates for PCSSs, including silicon (Si) [8], gallium arsenide (GaAs) [9], silicon carbide (SiC) [10], gallium nitride (GaN) [11], [12], and diamond [13]
Summary
P HOTOCONDUCTIVE semiconductor switches (PCSSs) have been investigated as promising optoelectronic devices for pulsed power systems since the late 1970s [1]. The conductivity of PCSSs operating in the linear mode is proportional to the incident optical power, while the avalanche process dominates in the nonlinear mode, which is called the high gain mode [6], [7]. Even though earlier works on GaAs-based lateral PCSSs reported high-voltage and high-current switching performances [14]–[16], there have been research activities to improve the operating voltages of PCSSs using wide bandgap semiconductors. The excellent material properties of SiC, such as wide bandgap energy (3.23 eV), high breakdown field (2–4 MV/cm), high electron saturation velocity (2.0 × 107 cm/s), and high thermal conductivity (4.9 W·cm−1K−1), have driven active studies of SiC-based PCSSs in search of higher voltage, higher current, and more stable operations [17]–[19]
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