An optoelectronic device comprising a substrate comprising a groove having a first and a second side. The first and second sides of the groove are each coated with a conductor material and a semiconductor material. The semiconductor material on the first side of the groove and the conductor material on the second side of the groove are in contact with another semiconductor material in the groove. At the second side of the groove there is a gap between the semiconductor material on the second side of the groove and the another semiconductor material in the groove.