Chapter 10 - Some Novel Devices

Abstract

This chapter introduces some of the new semiconductor devices such as cold cathode. It is a device for electron field emission that replaces the hot filament in vacuum electronics. High power high frequency devices such as the traveling wave tube are still the backbone of the high power amplifier. Recently, a new type of cold cathode has come on the scene, field emission with resonant tunneling , and a scheme that involves placing a quantum well structure at the surface of a semiconductor with a fairly low work function such as the GaN. This has opened the door to a whole class of schemes such as embedding CdSe in porous silicon for nonlinear optics at low power. This is not achievable with quantum wells because quantum confinement in one dimension leaves a large two dimensional density of states in the transverse degree of freedom. Optical transition still involves nearly the same number of oscillators, while in quantum dots (QD), being zero dimensional system, optical transition involves only one state. The chapter emphasizes that multipole potentials are short ranged.