Electronic device with enhancement mode gallium nitride transistor, and method of making same

An electronic device, comprising:

• a substrate;
• a buffer structure over the substrate;
• a first gallium nitride layer over the buffer structure;
• an aluminum gallium nitride layer on the first gallium nitride layer;
• a gate structure having a second gallium nitride layer, a third gallium nitride layer, and a gate contact, wherein:
• the second gallium nitride layer is directly on the aluminum gallium nitride layer;
• the third gallium nitride layer is directly on the second gallium nitride layer;
• and
• the gate contact is directly on the third gallium nitride layer;
• a drain contact spaced apart from the gate contact;
• and
• a source contact spaced apart from the gate contact and from the drain contact;
• wherein the third gallium nitride layer has a first peak p-type dopant concentration less than 1×1017 atoms/cm3;
• and
• wherein the second gallium nitride layer has a second peak p-type dopant concentration that is more than 10 times greater than the first peak p-type dopant concentration.