Method for fabricating high electron mobility transistor

A method for fabricating a high electron mobility transistor (HEMT), comprising:

• forming a buffer layer on a substrate;
• forming a barrier layer on the buffer layer;
• forming a p-type semiconductor layer on the barrier layer, wherein the p-type semiconductor layer comprises p-type gallium nitride (pGaN);
• forming a passivation layer on and directly contacting the p-type semiconductor layer and the barrier layer, wherein the passivation layer directly contacts a top surface and a sidewall of the p-type semiconductor layer, and a top surface of the barrier layer;
• performing an ion implantation process to implant silicon atoms into the p-type semiconductor layer to form a hole injection buffer layer (HIBL) comprising a silicon layer for neutralizing magnesium acceptors on a surface of the p-type semiconductor layer, wherein the silicon atoms of the ion implantation process are not implanted into the barrier layer and the buffer layer, and wherein the passivation layer remains covering the top surface of the p-type semiconductor layer while the ion implantation process is performed;
• and
• forming a gate electrode on the HIBL.