Conductivity type conversion of p-type CuInSe2 due to hydrogenation

The surface of p-type CuInSe2 single crystals prior to and after low energy hydrogen ion implantation at increased substrate temperature has been investigated by X-ray photoelectron spectroscopy (XPS) and Raman measurements. A shift of the Fermi-level by 500 meV closer to the conduction band after the hydrogen exposure has been observed for CuInSe2, oxidized by storage in air. The same behavior was observed for a clean surface prepared in ultra-high vacuum (UHV) by cleavage of CuInSe2. This observation supports the previously suggested type conversion from p- to n-type of the surface of CuInSe2. The conversion is explained by the passivation of Cu vacancies and hydrogen on and interstitial site. For the oxidized sample, the re-activation of oxygen passivated Se vacancies might influence the type conversion additionally. Raman spectroscopy did not reveal any lattice damage after implantation at 300°C sample temperature.