Semiconductor structure and method of forming the same

A semiconductor structure comprising:

• a gallium nitride (GaN) layer disposed on a substrate;
• an aluminum gallium nitride (AlGaN) layer disposed on the GaN layer;
• a gate disposed on an upper surface of the AlGaN layer;
• a source feature and a drain feature disposed on opposite side of the gate, each of the source feature and the drain feature comprising a corresponding intermetallic compound at least partially embedded in the AlGaN layer, wherein each intermetallic compound has a non-flat top surface;
• and
• a dielectric cap layer over the upper surface of the AlGaN layer, at least a portion of the dielectric cap layer being sandwiched between a portion of the intermetallic compounds and the AlGaN layer.

A method of forming a semiconductor structure, the method comprising:

• providing a first III-V compound layer;
• epitaxially growing a second III-V compound layer on the first III-V compound layer, wherein an interface is defined between the first III-V compound layer and the second III-V compound layer;
• partially etching the second III-V compound layer to form two recesses in the second III-V compound layer;
• forming two metal features each in a corresponding one of the two recesses;
• annealing the metal features to form corresponding intermetallic compounds, each of the intermetallic compounds contacting a carrier channel located at the interface;
• and
• forming a gate on the second III-V compound layer between the intermetallic compounds.