Enhancement-mode GaN HFET including ScAIN and method of manufacturing the same

1 . A semiconductor device comprising:

a substrate;

a gallium nitride layer disposed over the substrate;

an aluminum gallium nitride layer disposed over the gallium nitride layer, wherein the aluminum gallium nitride layer provides a wet etch stop once a surface of the aluminum gallium nitride layer is exposed to extend a gate recess through a scandium aluminum nitride layer disposed over the aluminum gallium nitride layer;

a source in contact with the gallium nitride layer;

a drain spaced from the source, wherein the drain is in contact with the gallium nitride layer; and

a gate that extends through the scandium aluminum nitride layer and is in contact with a surface of the aluminum gallium nitride layer to configure the semiconductor device for enhancement mode operation.

2 . The semiconductor device of claim 1 wherein the semiconductor device is a field-effect transistor having the enhancement mode of operation.

3 . The semiconductor device of claim 1 wherein the scandium aluminum nitride layer is between 20 Å and 500 Å thick.

4 . The semiconductor device of claim 1 further comprising a hard mask disposed over the scandium aluminum nitride layer.

5 . The semiconductor device of claim 4 wherein the hard mask is a silicon nitride layer.

6 . The semiconductor device of claim 1 wherein the scandium aluminum nitride layer is made of Sc x Al (1-x) N with x being between 0.1 and 0.3.

7 . The semiconductor device of claim 1 wherein the aluminum gallium nitride layer is made of Al y Ga (1-y) N with y being between 0.05 and 0.4.

8 . The semiconductor device of claim 4 wherein the hard mask is made of silicon oxide.

9 . A method of fabricating a semiconductor device comprising:

providing a substrate with a gallium nitride layer disposed over the substrate, an aluminum gallium nitride layer disposed over the gallium nitride layer, and a scandium aluminum nitride layer disposed over the aluminum gallium nitride layer,

disposing a hard mask over the scandium aluminum nitride layer;

forming a source in contact with the gallium nitride layer;

forming a drain spaced from the source, wherein the drain is in contact with the gallium nitride layer;

dry etching a gate recess through the hard mask; and

wet etching through the scandium aluminum nitride layer until the wet etching inherently stops once a surface of the aluminum gallium nitride layer is exposed to extend the gate recess through the scandium aluminum nitride layer.

10 . The method of claim 9 further comprising forming a gate that extends through the scandium aluminum nitride layer and is in contact with the surface of the aluminum gallium nitride layer.

11 . The method of claim 10 wherein the gate is made of metal.

12 . The method of claim 10 further comprising disposing metal contacts over the source and drain, respectively.

13 . The method of claim 10 wherein the semiconductor device is a field-effect transistor having an enhancement mode of operation.

14 . The method of claim 9 wherein the scandium aluminum nitride layer is made of Sc x Al (1-x) N with x being between 0.1 and 0.3.

15 . The method of claim 9 wherein the aluminum gallium nitride layer is made of Al y Ga (1-y) N with y being between 0.05 and 0.4.

16 . The method of claim 9 wherein the hard mask is made of a nitride compound.

17 . The method of claim 16 wherein the nitride compound is silicon nitride.

18 . The method of claim 9 wherein the hard mask is made of an oxide compound.

19 . The method of claim 18 wherein the oxide compound is silicon oxide.

20 . The method of claim 9 wherein the wet etching is performed using a mixture of sulfuric acid and hydrogen peroxide.