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The breakdown behavior of a V-doped 4H silicon carbide photoconductive switch with a transparent electrode under a high electric field is studied. The device is triggered by a laser pulse below the bandgap wavelength with a repetition rate of 100 Hz. The light peak-power of the laser pulse reaches hundreds of kW, and the bias voltage is increased from 10 to 20 kV. With the accumulation of the number of pulses, the device shows breakdown behavior. Through the microscopic diagnosis of damaged and breakdown devices, according to the analysis of theoretical and simulation results, the breakdown of the device is due to the interaction between the laser and the aluminum doped zinc oxide transparent electrode on the device surface, resulting in the melting of the transparent electrode. The direct illuminate of the laser can form a field enhancement effect at the junction of the substrate and the transparent electrode, resulting in the damage of the device and the formation of pre-breakdown. Finally, the breakdown of the device inevitably occurs.

Photoconductive semiconductors operating in linear mode can be used for adaptive high-power microwave (HPM) generators by modulating incident light. This paper presents the design scheme and preliminary test results of a narrowband kW class adaptive photonic microwave generator by employing a widebandgap semi-insulating 6H-SiC photoconductive semiconductor and a burst-mode laser. The experimental scheme of the generator is described along with the circuit simulation of the radio frequency generator. The laser operated at a wavelength of 532 nm with a pulse width of 100 ns and a repetition rate of 100 Hz. The laser modulates the frequencies of the generated microwave, and preliminary tests are conducted in the frequency range of 0.8-1.2 GHz. The maximum output microwave power of the designed scheme reaches up to 2.6 kW when the bias voltage is 10 kV. The results confirm that this method can be used for high-power frequency-adjustable microwave signal generation. The microwave source system presented in this paper has continuously adjustable frequency and flexible waveform control.

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