Chapter 7 - Erbium in silicon and silicon-germanium

Abstract

This chapter deals with the erbium-doped silicon system and erbium-doped silicon-germanium. The introductory section begins with a brief description of the motivation for making a silicon light emitter and the basic concepts of excitation and recombination in these systems. Silicon is an indirect band gap semiconductor, and so the probability of radiative recombination between the bands is extremely low. The concept of zone folding attempts to overcome this feature by using a thin multilayer structure of silicon and silicon-germanium, to modify the band structure are also discussed. The whole concept of erbium luminescence in silicon is to use the energy from electron-hole excitation, either via a p-n junction or optical excitation across the band gap, to excite the erbium ion in the silicon lattice and thus produce luminescence. Furthermore, the chapter also reviews the relevant properties of erbium and examines the way erbium can be incorporated into silicon and silicon germanium and the lattice sites it occupies, and examines the electrical activity of erbium in silicon. This chapter concludes by reviewing device issues associated with this material system.