High electron mobility transistor and method for fabricating the same

1. A high electron mobility transistor (HEMT), comprising:

a buffer layer on a substrate;

a p-type semiconductor layer on the buffer layer;

a first barrier layer between the buffer layer and the p-type semiconductor layer;

a second barrier layer adjacent to two sides of the first barrier layer, wherein the first barrier layer and the second barrier layer comprise different thicknesses, bottom surfaces of the first barrier layer and the second barrier layer are coplanar, both the first barrier layer and the second barrier layer are made of III-V semiconductor, and a sidewall of the first barrier layer aligned with a sidewall of the p-type semiconductor layer is perpendicular to a top surface of the buffer layer and contacting a sidewall of the second barrier layer directly;

a gate electrode on the p-type semiconductor layer; and

a source electrode and a drain electrode adjacent to two sides of the gate electrode on the buffer layer.

2. The HEMT of claim 1 , wherein the first barrier layer and the second barrier layer comprise Al x Ga 1-x N.

3. The HEMT of claim 2 , wherein the first barrier layer and the second barrier layer comprise different concentrations of Al.

4. The HEMT of claim 2 , wherein a concentration of Al of the first barrier layer is less than a concentration of Al of the second barrier layer.

5. The HEMT of claim 1 , wherein a thickness of the first barrier layer is less than a thickness of the second barrier layer.

6. The HEMT of claim 1 , wherein sidewalls of the p-type semiconductor layer and the second barrier layer are aligned.