Ballistic transport in hot-electron transistors

Abstract

We demonstrate that the performance of hot-electron transistors and other ballistic devices can be greatly improved if a focused beam of energetic electrons is injected into the active region of a high-speed device. The results of the Monte Carlo simulations of 72 000 electrons show that the angular distribution of electrons arriving at the collector of a hot-electron transistor is sharper since those electrons injected into the base under large angles primarily contribute to the base current. Our calculations also confirm that ballistic motion may be considerably enhanced by the built-in electric field in the base region. Based on these results, we propose a new device—the double base hot-electron transistor—where the first base acts as an ‘‘electron gun’’ focusing and accelerating the electron beam, which is then injected into the second (active) base where an input signal is applied. Our calculations show that the mean transit time of electrons traversing the active base can be considerably reduced and that the fraction of energetic electrons reaching the collector can be significantly increased in the proposed double-base hot-electron transistor in comparison with a conventional hot-electron transistor.