Photoelectric property of LaAlO_3-δ/Si heterojunctions with different oxygen contents

Three oxide heterojunctions made of LaAlO_3-δ/Si are fabricated under various oxygen pressures by laser molecular-beam epitaxy. They all show nonlinear and rectifying current - voltage characteristics, and the distinct difference in rectification behaviour among them. Their photoelectric properties are examined by a visible HeNe laser and an ultraviolet Hg lamp. We find that their photovoltaic responses are closely related to the oxygen contents in the LaAlO_3-δ films. The junction fabricated under the lower oxygen pressure has a higher photovoltaic sensitivity. The possible mechanism is suggested based on the band structure of the p - n heterojunction.