Method Of Forming A GaN Sensor Having A Controlled And Stable Threshold Voltage

A method of fabrication of a gallium nitride (GaN) based sensor comprising:

• forming a gate dielectric layer over a GaN hetero-structure that comprises a GaN layer formed over a substrate and a first barrier layer formed over the GaN layer;
• forming a first mask over the gate dielectric layer, wherein the first mask includes first openings that define locations of source and drain contact regions;
• etching the gate dielectric layer and the first barrier layer through the first openings in the first mask, thereby forming source and drain contact openings;
• removing the first mask;
• then
• forming a metal layer over the gate dielectric layer, wherein the metal layer extends into the source and drain contact openings;
• forming a second mask over the metal layer;
• etching the metal layer, the gate dielectric layer and the GaN heterostructure through the second mask, wherein a region of the GaN heterostructure is exposed;
• and
• thermally activating the metal layer in the source and drain contact openings.