Optimum design of electron beam-semiconductor linear low-pass amplifiers—Part I: Bandwidth and rise time

This paper begins with a brief description of the basic electrical characteristics and principles of operation of the lumped-element electron-beam-excited-semiconductor amplifier. It is shown that stable current gains of several thousand may be obtained through the interaction of a 10-keV electron beam with a shallow reverse-biased p-n junction device (semiconductor target). Simplest case analyses of the transient-response rise time and RF gain and bandwidth are presented for an idealized nondistributed target structure, using the assumptions of shallow beam penetration across the drift region, carrier transport with a constant velocity, and a resistive load impedance. The dynamic response is shown to be determined jointly by the carrier transit time and the target capacitance in such a way that it is possible to optimize the target rise time or bandwidth by appropriate choices of drift-region width. The optimum drift-region width and the ultimate rise times and bandwidths are evaluated in terms of the target area, load impedance, carrier drift velocity, and semiconductor dielectric constant. It is shown that lumped-element semiconductor targets can readily be designed for subnanosecond rise times and broad bandwidths without compromise of the high current gain possible in these devices.