Microwave oscillations from silicon planar diodes

We have observed microwave oscillations in reverse biased silicon planar epitaxial diodes. The p-i-n structure was not unlike that suggested by Read, but the diodes were operated well beyond breakdown in the manner described by Johnston et al. The oscillation was continuous in the range .8 to 3.5 Gc and pulsed operation was used up to 28 Gc. The lindwidth at L band was less than 60 kc. The continuous power was 1 mW and relatively independent of frequency. The efficiency was .15%. The peak power under pulsed operation was 15 mW.