Vertical hemt and a method to produce a vertical hemt

A method for producing a vertical transistor, the method comprising:

• providing a base layer wherein the base layer comprises a substrate;
• forming a vertical electron transport layer on the base layer, the vertical electron transport layer comprises a vertically conducting aperture and a supporting material laterally enclosing or defining the vertically conducting aperture, the supporting material is configured to be a current blocking layer, wherein the forming of the vertical electron transport layer comprises:
• epitaxially forming the vertically conducting aperture, and
• depositing the supporting material after formation of the vertically conducting aperture;
• depositing a heterostructure on the vertical electron transport layer and in contact with the vertically conducting aperture, the heterostructure comprising an AlGaN-layer and a GaN-layer together forming a heterojunction;
• forming at least one source contact in contact with the heterostructure, the at least one source contact being laterally offset from the vertically conducting aperture;
• forming a gate contact in contact with the heterostructure and arranged above the vertically conducting aperture;
• and
• forming a drain contact in contact with the vertically conducting aperture;
• wherein the vertically conducting aperture is forming an electron transport channel between the drain contact and the heterostructure.