Recent results obtained with epitaxial gunn effect oscillators

Continuous wave oscillations with fundamental frequencies from 3 to 35 Gc have been observed using Gunn effect oscillators constructed from epitaxially grown n-GaAs of various thicknesses between 4 and 40µ on n⁺- substrates. Device fabrication techniques will be discussed. The material used in these devices is an n⁺⁺-n-n⁺GaAs sandwich structure prepared by epitaxial techniques. The highest CW power levels obtained to date are 65 mw at 5 Gc, 140 mw at 6.5 Gc, 110 mw at 11 Gc, 100 mw at 14 Gc, 6.5 mw at 23 Gc, and 1 mw at 35 Gc. For samples operating below 16 Gc, the efficiency ranges between 2 and 3 percent. The oscillators can be tuned approximately an octave in frequency-by the external cavity. The frequency is relatively insensitive to bias voltage: its electronic tuning sensitivity-is about 25 Mc/volt at frequencies near 14 Gc. Preliminary measurements at 6 Gc indicate a double sideband AM carrier-to-noise ratio of about 120 db and an FM noise deviation of about 20 cps rms, both measured in a 1 kc bandwidth at 100 kc from the carrier.