A power transistor includes a first terminal, a second terminal and a control terminal. A support layer is formed of a first material having a first bandgap. An active region is formed of a second material having a second bandgap wider than the first bandgap, and is disposed on the support layer. The active region is arranged to form part of a current path between the first and second terminal in a forward mode of operation. The active region includes at least one pn-junction.