B.S.T.J. Briefs: A Low-Noise Metal-Semiconductor-Metal (MSM) Microwave Oscillator

Low-noise microwave CW oscillations have been obtained from metal-semiconductor-metal (MSM) structures made from a 10-/xm thin slice of silicon sandwiched between two PtSi Schottky barrier contacts. Microwave CW power up to 50 mW has been obtained at 5 GHz with efficiency up to 1.8 percent. The FM noise measure 1 MHz from the carrier is 22.8 dB which is considerably lower than that of a silicon avalanche oscillator. The mechanisms responsible for the microwave oscillation are (i) the exponential increase of the local carrier population due to injection of minority carriers at the forward-biased contact and (ii) the transit-time delay of injected carriers traversing the depletion region. By optimizing material and device parameters, it is believed that higher efficiency and higher power microwave oscillations can be obtained from the MSM and its related structures with the inherent low-noise characteristics.