Temperature dependent spectroscopic study of the electronic structure of phosphorus in-type CVD diamond films

摘要

In this work we used the quasi-steady-state photocurrent method and photothermal ionisation spectroscopy (PTIS) to study the electronic structure of the P-related level in n-type phosphorus doped CVD diamond. Previously, we reported the existence of two optically active defect levels, labelled X{sub}(P1) and X{sub}(P2) in the bandgap of these P-doped layers. X{sub}(P2) appeared to be only present in films showing high resistivity. Here we present a detailed PTIS and photocurrent study of the photoionisation cross-section, from liquid helium up to room temperature. At low temperatures, samples containing only the X{sub}(P1) defect show a phonon-induced oscillatory photoconductivity giving information about the electronic structure of this defect. Additionally, with PTIS a sharp maximum was detected around 565 meV, originating from a thermal promotion of charge carriers from an excited state of the phosphorus-related level into the conduction band. We also discuss different models for the optical ionisation cross-section of the P-related level (e.g. shallow level deep level).