High electron mobility transistor (hemt) device and method of forming same

A method comprising:

• forming a GaN layer over a substrate;
• forming a first AlGaN layer over the GaN layer;
• forming a p-doped GaN layer over the first AlGaN layer;
• blanket depositing a dielectric material over the p-doped GaN layer and the first AlGaN layer;
• removing a portion of the dielectric material from over a topmost surface of the first AlGaN layer, a remaining portion of the dielectric material extending along a topmost surface and sidewalls of the p-doped GaN layer forming a passivation layer;
• and
• forming a second AlGaN layer over the first AlGaN layer, the second AlGaN layer having a greater aluminum content than the first AlGaN layer.

A device comprising:

• a substrate;
• a GaN layer over the substrate;
• a first AlGaN layer over the GaN layer;
• a p-doped GaN layer over the first AlGaN layer, a width of the p-doped GaN layer being less than a width of the first AlGaN layer;
• and
• a second AlGaN layer over the first AlGaN layer, the second AlGaN layer having a greater aluminum content than the first AlGaN layer.