Generation of powerful microwave voltage oscillations in a diffused silicon diode

The mechanism of the generation of powerful microwave voltage oscillations in a diffused silicon diode is studied. A reverse current 2 kA in amplitude is passed through a 0.5-cm$^2$ diode with a structure thickness of 320 $\mu$m, a $p$–$n$ junction depth of 220 $\mu$m. At an average diode voltage of $\sim$ 300 V and a microwave pulse duration of $\sim$ 200 ns, the maximum voltage swing reaches 480 V. The oscillation frequency lies in the range 5 to 7 GHz; the power of the microwave pulse component is $\sim$ 300 kW. A theoretical consideration shows that voltage oscillations are caused by periodically repeating processes of breakdown and structure filling with plasma followed by its removal by the reverse current. The frequency and voltage swing are controlled by the current density and dopant-concentration gradient in the vicinity of the $p$–$n$ junction.