As a novel type of solid-state devices, photoconductive switches (PCSS) offer remarkable characteristics such as high power output (~MW), low jitter (~ps), ultra-fast switching time (~ps), and high repetition rates (>MHz). These advantages have led to their widespread application in diverse fields including pulsed power electronics, high-power microwave technology, and bioengineering. Compared to conventional photoconductive switches that rely on external energy storage capacitors, silicon carbide (SiC)-based integrated photoconductive switches exhibit superior performance, including faster rise times and narrower pulse widths, making them especially suitable for high-frequency and high-voltage signal transmission applications. This study systematically examines the performance variations of the energy storage capacitor unit within the integrated switch device under varying frequencies and under high-temperature, high-humidity conditions. Experimental results reveal that electrical breakdown in the energy storage capacitor unit under high electric field strength is primarily attributed to threading screw dislocation (TSD) presenting in the semi-insulating SiC substrate. Furthermore, simulation results confirm the correlation between the spatial distribution of screw dislocations and the voltage withstand capability of the energy storage capacitor unit. It is anticipated that the findings of this study will provide valuable insights for optimizing the structural design of integrated photoconductive switches and enhancing their performance under high electric field conditions.

In this study, we systematically investigated the conductive properties of integrated photoconductive switches. The experimental procedure was as follows: integrated photoconductive switch devices with varying capacitance values were fabricated, all with an electrode spacing of 1.5 mm. Initially, devices with capacitance values of 14 pF and 25 pF were tested. The experimental results demonstrated that the integrated photoconductive switch with a capacitance of 25 pF exhibited superior voltage conversion efficiency. To further evaluate the stability of the integrated switch device, the performance of the 25 pF energy storage capacitor unit was examined under high-frequency, high-temperature, and high-humidity conditions. High-frequency stability was assessed using an LCR meter (Keysight E4980A), while aging tests under high-temperature and high-humidity were conducted under reverse bias using a dedicated test system (DEVR-H3). Subsequently, the behavior of the 25 pF integrated photoconductive switch under high electric field strength was investigated. The breakdown mechanism was analyzed by integrating experimental data with theoretical simulations. Additionally, the correlation between the distribution of screw dislocations and the voltage withstand capability of the energy storage capacitor unit was explored.

This study developed a SiC photoconductive switch device that combines switching and capacitor functions. It features an ultra-fast rise time (211 ps, measured from 10% to 90%) (Table 1), a minimum on-resistance of 5.3 Ω, and an output power of 6.5 MW (Fig. 3). Experimental results demonstrate that the energy storage capacitor unit integrated within the SiC photoconductive switch device exhibits high stability under high-frequency, high-temperature, and high-humidity conditions (Fig. 2). Through a combination of experimental and simulation approachs, it was determined that screw dislocations in the 4H-SiC substrate are the primary cause of electrical breakdown in the energy storage capacitor unit under high electric field strengths. Both experimental and simulation results confirm a clear correlation between the breakdown voltage and the distribution of screw dislocations (Figs. 4?6).

In this study, an integrated device based on 4H-SiC that combines photoconductive switching functionality was fabricated. The energy storage capacitor unit demonstrated high stability under high-frequency, high-temperature, and high-humidity conditions. The integrated photoconductive switching device achieved a maximum voltage conversion efficiency of 90.2%, a rise time of 211 ps, and a maximum output power of 6.5 MW. The results clearly indicate that screw dislocations in the 4H-SiC substrate are the primary cause of electrical breakdown in the energy storage capacitor unit under high electric field strengths. Through a combination of experimental and simulation approaches, the correlation between breakdown voltage and the distribution of screw dislocations was analyzed. Reducing the dislocation density in the 4H-SiC substrate is an effective strategy to enhance the voltage withstand capability of integrated photoconductive switch devices with integrated switching and capacitor functions. Additionally, avoiding the placement of energy storage capacitor units in regions with TSD aggregation during device manufacturing presents another viable approach to improve the voltage endurance of the switch.