Effect of hydrogen plasma treatment on the electrical properties of sputtered N-doped cuprous oxide films

Cuprous oxide (Cu2O) is a direct-gap semiconductor with band-gap energy of 2.0 eV and is regarded as one of the most promising materials for application in photovoltaic cells. Practical application has not been achieved to date because of the difficulty of controlling its electrical properties such as reducing the resistivity. It is known that nitrogen doping is one of the effective methods to reduce the resistivity of cuprous oxide films. In this study, N-doped cuprous oxide films have been deposited onto Corning 1737 at a constant substrate temperature of 350 °C using a magnetron co-sputtering process in a mixture of oxygen and argon gases. It was found that the hole carrier concentration of nitrogen-doped cuprous oxide films increased from 9.0 × 1017 cm−3 to 4.0 × 1018 cm−3 as the nitrogen flow rate increased from 4 to 12 ml min−1. The lowest resistivity of Cu2O film doped with nitrogen obtained in this study was 14.8 Ω cm and further downed to a value of 9.1 Ω cm after 1 min of hydrogen plasma treatment. Because the mobility of the carrier is almost constant, it is believed that the hydrogen plasma treatment may terminate the dangling bonds of Cu and result in increasing the carrier concentration which leads to decrease in the resistivity of the Cu2O films.