Gallium nitride semiconductor devices and method making thereof

A transistor device, comprising:

• a substrate;
• a gallium nitride (GaN) layer disposed over the substrate;
• an electron supply layer disposed onto the GaN layer, wherein the electron supply layer has a larger bandgap than the GaN layer, so as to form a hetero-junction therebetween;
• an aluminum nitride (AlN) etch stop layer disposed onto and in direct contact with the electron supply layer, wherein the AlN etch stop layer is configured to stop an etching process from etching the electron supply layer;
• and
• a source contact and a drain contact abutting the electron supply layer and the AlN etch stop layer, wherein a bottom surface of the source contact, a bottom surface of the drain contact and a bottom surface of the AlN etch stop layer are coplanar and contact a to surface of the electron supply layer;
• a gate structure disposed at a position abutting the AlN etch stop layer, wherein the gate structure comprises a group III-V semiconductor material located on to of and in direct contact with the AlN etch stop layer, and a gate metal layer located on top of and in direct contact with the group III-V semiconductor material, and
• wherein the AlN etch stop layer has a larger bandgap than the electron supply layer and the gate structure.

A gallium nitride (GaN) transistor device, comprising:

• a substrate;
• a gallium nitride (GaN) layer disposed over the substrate;
• a layer of aluminum gallium nitride (AlGaN) disposed onto and in direct contact with the GaN layer;
• a layer of aluminum nitride (AlN) disposed onto and in direct contact with the layer of AlGaN, wherein the layer of AlN is configured to stop an etching process from etching the layer of AlGaN;
• a source contact and a drain contact abutting the layer if AlGaN and the layer of AlN, wherein a bottom surface of the source contact, a bottom surface of the drain contact and a bottom surface of the layer of AlN are coplanar and contact a top surface of the layer of AlGaN;
• a layer of doped gallium nitride (GaN) disposed onto and in direct contact with the layer of AlN;
• and
• a layer of gate metal disposed onto and in direct contact with the layer of doped GaN.