Frequency response of bipolar junction transistors after electron-beam irradiations

The small-signal frequency response of silicon bipolar junction transistors was measured after the devices were irradiated with electrons below the displacement threshold. The measurements indicated that the high-frequency response of transistors is unchanged by electron irradiation, even though the low-frequency gain is degraded. Whereas process variations intended to change either the gain or cutoff frequency of transistors inevitably affect both, the electron-beam irradiation changes only the gain, giving a clear demonstration of the fact that the cutoff frequency is determined by the physical base transit time. As a practical consequence, the result implies that electron-beam irradiation has relatively little effect on circuit performance