Chapter 3 Radiative Isoelectronic Impurities in Silicon and Silicon-Germanium Alloys and Superlattices

Abstract

Publisher Summary This chapter focuses on recent investigations of the radiative decay of excitons bound to isoelectronic impurities in Si, SiGe alloys, and SiGe/Si superlattices. Because the electron and hole that define the exciton are localized at an impurity site, recombination is not subject to the k-conservation selection rule. The radiative decay of isoelectronic-bound excitons (IBEs) can therefore produce intense no-phonon lines at subbandgap photon energies. Relatively few IBE systems have been demonstrated in group IV semiconductors, so the following sections should be interpreted as describing the current status of work in progress. An isoelectronic impurity is, in its simplest substitutional form, isovalent with the host crystal. Examples of substitutional isoelectronic atoms for a group IV material such as Si would be any other element in the column: C, Ge, and Sn may each substitute for Si without influencing the number of valence electrons. They are electrically inactive in the sense that they do not influence the carrier density in the conduction or valence bands and therefore have a weak influence on the conductivity.