High electron mobility transistor 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, wherein a fluorine region is embedded in the AlGaN layer;
• an indium gallium nitride (InGaN) layer disposed on the AlGaN layer;
• a P-type GaN layer disposed on the InGaN layer;
• a source feature and a drain feature spaced apart and disposed on the AlGaN layer;
• a gate electrode disposed over the AlGaN layer between the source feature and the drain feature, wherein the gate electrode is overlying the fluorine region;
• and
• a portion of a gate dielectric layer disposed between the gate electrode and the AlGaN layer, wherein the portion of the gate dielectric layer substantially covers the P-type GaN layer.

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

• epitaxially growing a second III-V compound layer on a first III-V compound layer, the second III-V compound layer being a different composition than the first III-V compound layer, wherein a carrier channel is located between the first III-V compound layer and the second III-V compound layer;
• forming a source feature and a drain feature on the second III-V compound layer;
• forming a third III-V compound layer on the second III-V compound layer, wherein a diffusion barrier layer is located between the second III-V compound layer and the third III-V compound layer;
• depositing a gate dielectric layer on a portion of the second III-V compound layer and an entire top surface of the third III-V compound layer;
• treating the gate dielectric layer on the portion of the second III-V compound layer with fluorine and forming a fluorine in the second III-V compound layer under the gate electrode;
• and
• forming a gate electrode on the treated gate dielectric layer between the source feature and the drain feature.