Semiconductor layer structure

A method for producing a semiconductor layer structure, the method comprising:

• providing a Si substrate comprising a top surface;
• forming a first semiconductor layer on said substrate, the first semiconductor layer comprising a plurality of vertical nanowire structures, arranged perpendicularly to said top surface of said substrate, the first semiconductor layer comprising AlN;
• depositing a second semiconductor layer on the first semiconductor layer, laterally and vertically enclosing said nanowire structures, wherein the second semiconductor layer comprises AlxGa1-xN, wherein 0≤x≤0.95, the second semiconductor layer comprising at least two dislocations, each of the two dislocations propagating laterally from separate nanowire structures in an M-direction of a wurtzite crystal structure, the two dislocations being coalesced with each other;
• depositing a third semiconductor layer on said second semiconductor layer, the third semiconductor layer comprising AlyGa1-yN, wherein 0≤y≤0.95;
• and
• depositing a fourth semiconductor layer on said third semiconductor layer, the fourth semiconductor layer comprising GaN.