Photoluminescence study of reactive-ion-etched silicon: A new boron-related defect

Abstract

We report on the observation of a new boron-related line at 1.114 eV in the photoluminescence spectrum of reactive-ion-etched silicon. The defect is produced in highly boron-doped samples that are subject to low etch rates. A systematic study of the etch rate dependence indicates that the critical factor is the thermal instability of the defect to the localized heating produced during etching of the sample. Also of significance is the mobility of the defect-producing species relative to the etch rate. A comparison with similar etching techniques using noble gases implies a high penetration depth, which is clearly not one of simple thermal diffusion from the surface. The role of the reactant gas is also considered; the defect is shown to occur in samples etched with gases containing no common element. It is proposed that the formation of a complex occurs between boron and an intrinsic species mobilized by the etching process.