Silicon transit time avalanche diode

Experimental and theoretical work with avalanche transit time oscillators will be presented. Previously it was shown that diodes possessing high field regions in which avalanche occurs uniformly along the direction of current flow show a negative resistance. Experimental attempts have been made to construct such a model. Since electrons have larger ionization rates than holes in silicon, the structure gives a more uniform distribution of avalanche than does the structure. Thus units have been made by acceptor diffusion into an type epitaxial film. A typical structure which was analyzed numerically shows behavior quite similar to the idealized model. Microwave oscillations have been observed in almost all slices. Slices with similar impurity distribution often given quite different characteristics. This is believed to have to do with the uniformity of current flow. Units made from a "good" wafer show similar characteristics from unit to unit. One unit oscillated at 8.2 Gc with 7.7 mw output and an efficiency of 0.7%. Microwave reflection measurements, spectrum width of oscillations, low frequency noise measurements, and light emission are correlated with device parameters and fabrication methods. The microwave characteristics are compared with the analysis.