Lifetime control in silicon power devices by electron or gamma irradiation

High-frequency operation of silicon power rectifiers and thyristors is made possible by the controlled reduction of minority carrier lifetime in these devices. The irradiation of silicon power devices is discussed for electrons of 0.8 to 12-MeV energy and gammas from Co⁶⁰in terms of their effectiveness in altering device switching properties. A comparison is made with gold or platinum diffused devices. The best tradeoff of forward voltage drop and reverse recovered charge or reverse recovery time in diodes or turnoff time in thyristors is provided by gold diffusion. However, this advantage is somewhat offset by the high leakage in gold-diffused devices which limits their maximum operating temperature. In addition, irradiation provides the more precise, uniform, and reproducible method of lifetime control.