Effect of short-pulsed ion irradiation on the optical and electrical properties of pyrolytic boron nitride

Abstract

The effect of irradiation by carbon ions in the mode of short-pulsed ion implantation on the optical and electrical characteristics of graphite-like pyrolytic boron nitride was studied. The characteristics of the states of growth defects localized in the band gap change more significantly with an increase in the energy density of the ion beam, which is accompanied by the ordering of the electronic structure of the compound due to radiation – thermal annealing. Absorption spectra indicate the predominant effect of static disorder due to defects. Irradiation forms a defective semiconductor material with a maximum band gap of 3.3–3.45 eV, a current value of 2.65–2.83 eV for direct transitions and 1.1–1.8 eV for indirect transitions, and an absorption edge due to exponentially distributed states of 1.3–2.6 eV and 2.6–3.3 eV defects of different nature. Anion vacancies, their clusters and impurity-vacancy complexes make the main contribution to the material properties. Irradiation forms low – conducting dielectric layers with surface conductivity of mixed n– and p–type on the surface of a pyrolytic boron nitride. The conduction mechanism is determined by the activation exchange of charge carriers between the allowed bands and donor and acceptor levels due to radiation and growth defects. After irradiation, the Fermi level remains localized near the position characteristic of the pyrolytic boron nitride near the middle of the band gap.