Avalanche multiplication in c.a.t.t.s

The use of avalanche and transit-time effects in microwave transistor-like structures is being explored to provide increased gain and higher-frequency operation of 3-terminal semiconductor power amplifiers. The paper describes certain aspects of the avalanche-multiplication process of importance for understanding c.a.t.t. operation and for c.a.t.t. design. It is shown that n-p-n silicon c.a.t.t.s can be designed to operate with moderate charge multiplication without requiring a critical value of collector-base bias voltage. Space-charge effects reduce the actual multiplication at high injection levels. Avalanche-generated holes, returning to the emitter and base regions, have profound effects on the d.c. and r.f. characteristics of the c.a.t.t. These effects are qualitatively understood. Experimental results are reported on device impedances, gain and bandwidth in the 2.5¿¿4.0 GHz region.