Gallium nitride transistor with a doped region

An enhancement-mode high electron mobility transistor (HEMT), comprising:

• a gallium nitride (GaN) layer;
• a GaN-based alloy layer over the GaN layer, the GaN-based alloy layer having a side facing away from the GaN layer;
• a p-doped GaN layer positioned on the side of the GaN-based alloy layer, the p-doped GaN layer located in a gate region of the HEMT;
• a gate contact structure supported by the p-doped GaN layer;
• source and drain contact structures that are supported by the GaN-based alloy layer;
• and
• an n-doped region including at least a portion positioned in a drain access region of the enhancement-mode HEMT, the n-doped region extending from the side of the GaN-based alloy layer into the GaN layer, wherein:
• the GaN-based alloy layer extends from the gate region past an edge of the p-doped GaN layer toward the drain contact structure;
• the drain contact structure has a first edge facing the gate contact structure and a second edge opposite the first edge;
• the n-doped region has a first edge facing the gate contact structure and a second edge opposite the first edge;
• the first edge of the n-doped region is laterally closer to the gate contact structure than the first edge of the drain contact structure;
• and
• the second edge of the drain contact structure is laterally closer to the gate contact structure than the second edge of the n-doped region.

A depletion-mode high electron mobility transistor (HEMT), comprising:

• a gallium nitride (GaN) layer;
• a GaN-based alloy layer over the GaN layer, the GaN-based alloy layer having a side facing away from the GaN layer;
• a gate contact structure on the GaN-based alloy layer;
• source and drain contact structures that are supported by the GaN-based alloy layer;
• and
• an n-doped region including at least a portion positioned in a drain access region of the depletion-mode HEMT, the n-doped region extending from the side of the GaN-based alloy layer into the GaN layer, wherein:
• the drain contact structure has a first edge facing the gate contact structure and a second edge opposite the first edge;
• the n-doped region has a first edge facing the gate contact structure and a second edge opposite the first edge;
• the first edge of the n-doped region is laterally closer to the gate contact structure than the first edge of the drain contact structure;
• and
• the second edge of the drain contact structure is laterally closer to the gate contact structure than the second edge of the n-doped region.