Ultra-high withstand voltage (>120 kV cm^–1) sub-nanosecond (<0.5 ns) aluminum nitride photoconductive semiconductor switch

Pulsed power technology delivers stored electrical energy to load systems through single pulses or short pulses with controllable repetition rates, finding critical applications in domains including high-power lasers, shock radar, environmental engineering, and metal processing. Within pulsed power systems, high-power ultrafast switches rank second only to energy storage devices in importance, with their performance directly governing high-power pulse output characteristics and overall system reliability. Conventional switching predominantly employs gas-based devices such as Pseudospark switch, thyratrons, and ignitrons. Although utilized in high-power lasers, shock radar, and microwave sources, these exhibit substantial limitations, including excessive volume, prolonged turn-on delays, and significant temporal jitter, severely constraining advancements toward higher operating frequencies and enhanced precision in pulsed power systems. Photoconductive semiconductor switches (PCSS) leverage the photoconductive effect in semiconductor materials to achieve ultrafast response speeds and extremely low temporal jitter through laser triggering. Concurrently, inherent advantages including extended operational lifetime, compact structural design, and integration compatibility enable significant improvements in pulse control accuracy and power density. The operational principle of PCSS involves withstanding kilovolt-level voltages through either intrinsic breakdown strength or reverse-biased pn junction characteristics, followed by pulsed optical excitation generating abundant carriers within the semiconductor material. This rapidly reduces resistivity below the conduction threshold within picosecond-to-nanosecond timescales, enabling switch activation. The inaugural PCSS, fabricated in 1975, employed silicon (Si) as the base material. Subsequently, gallium arsenide (GaAs) superseded silicon as the primary research focus owing to its extremely short photogenerated carrier lifetime and wider bandgap (~1.42 eV), which confer superior ultrafast characteristics, higher voltage withstand capability, and increased power density; nevertheless, GaAs’s relatively low breakdown field strength and poor thermal conductivity manifest as defects including shortened service life in high-power applications. Recently, application demands across multiple fields have driven PCSS development toward miniaturization, integration, higher voltage withstand, and greater power handling. Maturation in ultrawide-bandgap semiconductor fabrication technologies has consequently established new pathways for high-performance PCSS advancement. Aluminum nitride (AlN), as an ultrawide-bandgap semiconductor material (bandgap ~6.2 eV), possesses exceptional properties including ultrahigh breakdown field strength, high thermal conductivity, and elevated electron saturation velocity. These characteristics enable ultrahigh voltage withstand capabilities without device failure caused by localized thermal breakdown, positioning AlN as a promising candidate for manufacturing high-power, ultrafast-response PCSSs. This study synthesized AlN single crystals via physical vapor transport (PVT), with material characterization performed using field-emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), and Raman spectroscopy. Analytical results confirmed preferentially oriented growth along the [002] crystallographic direction and excellent crystalline quality. Vertically configured PCSSs fabricated from this material underwent optoelectronic performance evaluation employing ultraviolet (UV) laser triggering. Testing demonstrated: sub-nanosecond rise times ( indicating significant potential for broadband signal output applications; minimal peak output voltage standard deviation confirming exceptional signal stability; and reliable operation under bias fields up to 120 kV cm–1. Analysis of output characteristics revealed increasing trends in both peak output voltage and output power with elevated bias field strengths and pulsed laser energy, demonstrating substantial potential for achieving enhanced power output capabilities.