High electron mobility transistor having reduced threshold voltage variation and method of manufacturing the same

A high electron mobility transistor, comprising:

• a substrate;
• a channel layer on the substrate,
• the channel layer being a GaN layer,
• the channel layer including a 2DEG channel and a depletion area;
• a first channel supply layer on the channel layer and corresponding to the 2DEG channel,
• the first channel supply layer defining an opening that exposes the depletion area;
• a depletion layer on the first channel supply layer and on the depletion area;
• a second channel supply layer between the depletion layer and the depletion area,
• the second channel supply layer including a portion that is on an upper surface of the first channel supply layer and extends over the 2DEG channel,
• an aluminum (Al) content of the second channel supply layer being different from an aluminum (Al) content of the first channel supply layer,
• a polarizability of the second channel supply layer being less than a polarizability of the first channel supply layer, and
• the first and second channel supply layers both including an aluminum compound;
• source and drain electrodes spaced apart on the first channel supply layer;
• and
• a gate electrode on the depletion layer, wherein
• the depletion layer is not directly in contact with the first channel supply layer, and
• the depletion layer is configured to remove a 2DEG that is generated in the depletion area of the channel layer by the second channel supply layer.