Photoluminescence Analysis of NTD-Silicon

Abstract

Crystalline Si, which is optically excited at low-temperature (∼4 K), exhibits luminescence characteristic of several states for nonequilibrium electrons and holes. A single electron-hole pair can bind into an exciton that is chargeless but free to move in the lattice. Also, such a free exciton (FE) can become bound to a neutral impurity atom and become a bound exciton (BE). The energy of the BE state is lower than that of the FE by its binding energy to the impurity. An exciton will be bound to every type of neutral impurity atom with a different binding energy. Thus, when an electron-hole pair in a FE or BE state recombines radiatively, it emits a photon whose energy uniquely identifies the type of impurity atom to which it was bound or indicates that it was unbound. Recent workl has shown that an exciton luminescence spectrum from optically excited Si at ∼4 K is a very sensitive indicator of the various types of dopant impurity atoms present in the crystal. More recent work2 explained the kinetics of exciton capture and emission from impurity atoms and laid the ground work for making exciton luminescence a quantitative measure of impurity concentrations in Si. In this paper we, first, use the kinetics model of Hammond and Silver2 to calculate the impurity concentration dependence of exciton luminescence intensities in Si and, second, report detailed measurements on NTD Si with known substitutional P concentrations.KeywordsLuminescence IntensityImpurity AtomFree ExcitonNonequilibrium ElectronExciton LuminescenceThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.