Semiconductor device with ferroelectric aluminum nitride
Techniques in accordance with embodiments described herein are directed to semiconductor devices including a layer of aluminum nitride AlN or aluminum gallium nitride AlGaN as a ferroelectric layer and a method of making a thin film of AlN/AlGaN that possesses ferroelectric properties. In a ferroelectric transistor, a thin film of AlN/AlGaN that exhibits ferroelectric properties is formed between a gate electrode and a second semiconductor layer, e.g., of GaN.
1. A method, comprising:
forming a layer of a first group-III nitride over a substrate, the first group-III nitride including a first in-plane interatomic distance between a group-III atom and a nitrogen atom, the first in-plane interatomic distance being larger than a second in-plane interatomic distance between an aluminum atom and a nitrogen atom in aluminum nitride; and
forming a layer of aluminum nitride over the layer of the first group-III nitride and in a same facet direction as the layer of the first group-III nitride, the layer of aluminum nitride having a thickness less than 20 nm.
2. The method of claim 1 , wherein the forming the layer of aluminum nitride includes a growth cycle of:
depositing an aluminum source precursor over the first group-III nitride;
removing unreacted molecules of the aluminum source precursor;
applying a plasma of a nitrogen source precursor;
removing unreacted molecules of the nitrogen source precursor; and
applying an argon plasma or a helium/argon mixture plasma.
3. A method, comprising:
forming a layer of a first group-III nitride over a substrate, the first group-III nitride including a first in-plane interatomic distance between a group-III atom and a nitrogen atom, the first in-plane interatomic distance being larger than a second in-plane interatomic distance between an aluminum atom and a nitrogen atom in aluminum nitride; and
forming a layer of aluminum nitride over the layer of the first group-III nitride, the layer of aluminum nitride having a thickness less than 20 nm,
wherein the forming the layer of aluminum nitride includes a growth cycle of:
depositing an aluminum source precursor over the first group-III nitride;
removing unreacted molecules of the aluminum source precursor;
applying a plasma of a nitrogen source precursor;
removing unreacted molecules of the nitrogen source precursor; and
applying an argon plasma or a helium/argon mixture plasma.
4. A method, comprising:
forming a layer of GaN over a substrate;
forming a layer of Al 1-x Ga x N directly over the GaN layer, the Al 1-x Ga x N layer having a ferroelectric property;
forming a gate electrode over the Al 1-x Ga x N layer; and
forming a source/drain structure over the GaN layer and adjacent to the gate electrode.
5. The method of claim 4 , wherein 0≤x≤0.4 in the Al 1-x Ga x N layer.
6. The method of claim 4 , wherein the source/drain structure is positioned over the Al 1-x Ga x N layer.
7. The method of claim 4 , wherein the Al 1-x Ga x N layer has a thickness ranging from about 1 nm to 20 nm.
8. The method of claim 4 , wherein the GaN layer also includes InN.
9. The method of claim 4 , wherein the substrate includes sapphire.
10. The method of claim 4 , wherein the substrate is silicon, and further comprising forming a nucleation layer between the silicon substrate and the GaN layer.
11. The method of claim 10 , wherein the nucleation layer is AlN.
12. A method, comprising:
forming a first layer of a first group-III nitride over a substrate;
forming a second layer of a second group-III nitride over the first group-III nitride layer, the second group-III nitride containing AlN and having a ferroelectric property; and
forming a first electrode over the second layer of the second group-III nitride.
13. The method of claim 12 , further comprising forming a second electrode contacting the first layer of the first group-III nitride.
14. The method of claim 13 , wherein the first group-III nitride is un-doped GaN and the second group-III nitride is ferroelectric AlGaN having a thickness less than 20 nm.
15. The method of claim 12 , further comprising forming a second electrode contacting the second layer of the second group-III nitride and spaced apart from the first electrode.
16. The method of claim 12 , further comprising forming a dielectric layer positioned between the first electrode and the second layer of the second group-III nitride.
17. The method of claim 12 , wherein the second layer of the second group-III nitride is AlGaN and has a thickness ranging from about 1 nm to about 20 nm.
18. The method of claim 12 , wherein the substrate includes sapphire.
19. The method of claim 12 , wherein the first layer of the first group-III nitride includes GaN.
20. The method of claim 12 , wherein the second group-III nitride is Al 1-x Ga x N with 0≤x≤0.4.