Methods for processing high electron mobility transistor (hemt)

A method for processing a semiconductor transistor, the semiconductor transistor including a substrate, an epitaxial layer, and a plurality of transistor components that are formed on the epitaxial layer, the method comprising:

• removing a portion of the substrate that is disposed below a portion of the plurality of transistor components, to thereby expose a portion of a bottom surface of the epitaxial layer;
• forming an insulating layer on the exposed portion of the bottom surface of the epitaxial layer, the insulating layer being made of an electrically insulating material;
• forming at least one via that extends from a bottom surface of the insulating layer to a bottom surface of at least one of the plurality of the transistor components;
• depositing at least one metal layer on the bottom surface of the insulating layer, on a side wall of the via and on the bottom surface of the at least one of the plurality of transistor components;
• and
• applying a solder paste to a bottom surface of the at least one metal layer.