The Study of Oxygen Thermal Donors in Silicon by Photothermal Ionisation Spectroscopy

Abstract

ABSTRACTIt is well known that Czochralski-grown silicon contains up to 2×1018 cm-3 oxygen atoms. When this silicon is annealed at 450°C a series of “thermal” donors are formed. In this work we present the results of a study of annealed Czcochralski-silicon samples by Photothermal Ionisation Spectroscopy and IR transmission measurements. All previously reported thermal donors, which occur in the spectral region above 330cm-1, and hove ionisation energies 53–69.3 meV, are observed by us. Also, our experimental results show the presence of at least three previously unreported thermally formed donor transition series below 330cm-1. Our results indicate that the ionisation energies of these new shallow thermal donors would be 36.3, 37.0 and 37.4 meV. Assignments are made by comparison of the energy differences between excited states to those predicted by the Effective Mass Theory.