Semiconductor devices with a compositionally graded layer, and methods of making and use thereof

1 . A device comprising:

a first electrode layer;

a first semiconductor layer comprising a first semiconductor material having a first bandgap;

a second semiconductor layer having a top surface, a bottom surface, and a thickness, the thickness being the average dimension from the top surface to the bottom surface;

wherein the second semiconductor layer comprises a second semiconductor material that varies across the thickness from the bottom surface to the top surface, such that the second semiconductor material has a compositional gradient with thickness from an initial composition having an initial band gap at the bottom surface to a final comparison having a final bandgap at the top surface, such that the second semiconductor layer has a bandgap that varies with thickness from an initial bandgap at the bottom surface to a final bandgap at the top surface, wherein the final bandgap is greater than the initial bandgap, and the final bandgap is greater than the first bandgap;

an optional dielectric layer; and

a second electrode layer;

wherein the first semiconductor layer is disposed on top of and in physical contact with the first electrode layer;

wherein the second semiconductor layer is disposed on top of and in physical contact with the first semiconductor layer, such that bottom surface of the second semiconductor layer is disposed on and in physical contact with the first semiconductor layer and the first semiconductor layer is disposed between and in physical contact with the first electrode layer and bottom surface of the second semiconductor layer;

when the optional dielectric layer is present, then:

the optional dielectric layer is disposed on top of an in physical contact with the second semiconductor layer, such that the second semiconductor layer is disposed between and in physical contact with the first electrode layer and the optional dielectric layer, the top surface of the second semiconductor layer being in physical contact with the optional dielectric layer and the bottom surface of the second semiconductor layer being in physical contact with the first semiconductor layer; and

the second electrode layer is disposed on top of and in physical contact with the optional dielectric layer, such that the optional dielectric layer is disposed between and in physical contact with the second electrode layer and the second semiconductor layer; and

when the optional dielectric layer is absent, then:

the second electrode layer is disposed on top of an in physical contact with the second semiconductor layer, such that the second semiconductor layer is disposed between and in physical contact with the second electrode layer and the first semiconductor layer, the top surface of the second semiconductor layer being in physical contact with the second electrode layer and the bottom surface of the second semiconductor layer being in physical contact with the first semiconductor layer.

2 . The device of claim 1 , wherein the first electrode layer comprises a Schottky contact layer.

3 . The device of claim 1 , wherein the first semiconductor material comprises Ga 2 O 3 , GaN, SiC, SnO, InP, or a combination thereof.

4 . The device of claim 1 , wherein the first semiconductor material comprises Ga 2 O 3 .

5 . The device of claim 1 , wherein the first semiconductor layer has an average thickness of from 1 nm to 500 μm.

6 . The device of claim 1 , wherein the first semiconductor layer has an average thickness of from 1 nm to 1 μm.

7 . The device of claim 1 , wherein the second semiconductor material comprises (Al x Ga 1-x ) 2 O 3 wherein x is from 0 to 1.

8 . The device of claim 7 , wherein x varies along the thickness the second semiconductor material from a first value to a second value, the second value being greater than the first value.

9 . The device of claim 1 , wherein the second semiconductor material comprises (Al x Ga 1-x ) 2 O 3 wherein x is from 0.25 to 1.

10 . The device of claim 1 , wherein the compositional gradient of the second semiconductor material comprises a linear gradient, a stepped gradient, an exponential gradient, a logarithmic gradient, or a combination thereof.

11 . The device of claim 1 , wherein the compositional gradient of the second semiconductor material comprises an exponential gradient, a logarithmic gradient, or a combination thereof.

12 . The device of claim 1 , wherein the thickness of the second semiconductor layer is from 1 nm to 1000 nm.

13 . The device of claim 1 , wherein the thickness of the second semiconductor layer is 1 nm to 100 nm.

14 . The device of claim 1 , wherein the optional dielectric layer is present.

15 . The device of claim 14 , wherein the optional dielectric layer has an average thickness of from 1 nm to 20 μm.

16 . The device of claim 14 , wherein the optional dielectric layer comprises BaTiO 3 .

17 . The device of claim 1 , wherein the optional dielectric layer is absent.

18 . The device of claim 1 , wherein the second electrode layer comprises an Ohmic contact layer.

19 . A method of making the device of claim 1 , wherein the method comprises depositing, in any order, the first electrode layer, the first semiconductor layer, the second semiconductor layer, the optional dielectric layer (when present), and the second electrode layer.