Radiation from a semiconductor target excited by an electron beam in a gas diode

Radiation from a semiconductor target excited by an electron beam in a gas-filled diode was investigated at different gas (air) pressures. Subnanosecond high-voltage pulses (up to 200 kV) were applied to the pointed cathode of the diode. The targets in the form of a 15 — 20-μm-thick single-crystal CdS film with reflecting coatings forming an optical cavity and 0.7 — 1-mm-thick ZnSe plates were used. As the air pressure increased from 0.1 to 5 Torr, a decrease in the amplitude and duration of laser radiation pulses from the targets was observed. Lasing (λ = 520 nm) of CdS targets terminated at pressures greater than 2.2 Torr. The laser pulse duration varied from 125 to 20 ps. The study of the dynamics of radiation from ZnSe targets (λ = 460 nm) at atmospheric pressure showed that when the gap between the target and the electrodes was 0.2 — 1 mm thick, an intense near-surface glow was observed that consisted of a few pulses with the duration from 20 to 100 ps, caused by runaway electrons. Investigations showed that the runaway electrons may play an essential role in the excitation of semiconductors by subnanosecond high-voltage pulses.