A method comprises providing a semiconductor structure comprising a substrate and a nanowire above the substrate. The nanowire comprises a first semiconductor material and extends in a vertical direction of the substrate. A material layer is formed above the substrate. The material layer annularly encloses the nanowire. A first part of the nanowire is selectively removed relative to the material layer. A second part of the nanowire is not removed. A distal end of the second part of the nanowire distal from the substrate is closer to the substrate than a surface of the material layer so that the semiconductor structure has a recess at the location of the nanowire. The distal end of the nanowire is exposed at the bottom of the recess. The recess is filled with a second semiconductor material. The second semiconductor material is differently doped than the first semiconductor material.