Ir photodetector with graphene and phase change layers and related methods

1 . An infrared (IR) photodetector comprising:

an electrically conductive layer;

a first dielectric layer over the electrically conductive layer;

a phase change material layer over the first dielectric layer, the phase change material layer having a thickness gradient with different phase transition temperatures;

first and second electrically conductive contacts coupled to the phase change material layer, the phase change material layer having a first height value adjacent to the first electrically conductive contact, and a second height value adjacent to the second electrically conductive contact, the second height value being different than the first height value;

a graphene layer over the phase change material layer and having a perforated pattern therein; and

circuitry configured to

apply a bias voltage between the first and second electrically conductive contacts, and

detect a sensing current in the phase change material layer caused by IR radiation received by the graphene layer and an intensity of the IR radiation, the IR radiation having a frequency range based upon the bias voltage.

2 . The IR photodetector of claim 1 wherein the bias voltage comprises a pulse train.

3 . The IR photodetector of claim 2 wherein the pulse train comprises a multi-level pulse train.

4 . The IR photodetector of claim 1 wherein the phase change material layer comprises vanadium oxide.

5 . The IR photodetector of claim 1 further comprising:

a transparent electrically conductive layer over the phase change material layer;

a second dielectric layer over the phase change material layer; and

a protective layer over the graphene layer.

6 . The IR photodetector of claim 5 wherein the first dielectric layer comprises a polymer layer; and wherein the second dielectric layer comprises silicon nitride.

7 . The IR photodetector of claim 1 wherein the perforated pattern comprises an array of elliptical holes.

8 . The IR photodetector of claim 1 wherein the graphene layer is configured to receive at least one of mid-wavelength IR (MWIR) radiation and long wavelength IR (LWIR).

9 . The IR photodetector of claim 1 wherein the electrically conductive layer comprises at least one of gold, silver, and platinum.

10 . An infrared (IR) photodetector comprising:

an electrically conductive layer comprising at least one of gold, silver, and platinum;

a first dielectric layer over the electrically conductive layer;

a phase change material layer over the first dielectric layer and having a thickness gradient with different phase transition temperatures;

first and second electrically conductive contacts coupled to the phase change material layer, the phase change material layer having a first height value adjacent to the first electrically conductive contact, and a second height value adjacent to the second electrically conductive contact, the second height value being different than the first height value;

a graphene layer over the phase change material layer and having a perforated pattern therein; and

circuitry configured to

apply a pulse train bias voltage between the first and second electrically conductive contacts, and

detect a sensing current in the phase change material layer caused by IR radiation received by the graphene layer, the IR radiation having a frequency range based upon the pulse train bias voltage.

11 . The IR photodetector of claim 10 wherein the pulse train bias voltage comprises a multi-level pulse train.

12 . The IR photodetector of claim 10 wherein the phase change material layer comprises vanadium oxide.

13 . The IR photodetector of claim 10 further comprising:

a transparent electrically conductive layer over the phase change material layer;

a second dielectric layer over the phase change material layer; and

a protective layer over the graphene layer.

14 . The IR photodetector of claim 13 wherein the first dielectric layer comprises a polymer layer; and wherein the second dielectric layer comprises silicon nitride.

15 . The IR photodetector of claim 10 wherein the perforated pattern comprises an array of elliptical holes.

16 . The IR photodetector of claim 10 wherein the graphene layer is configured to receive at least one of mid-wavelength IR (MWIR) radiation and long wavelength IR (LWIR).

17 . A method of making an infrared (IR) photodetector, the method comprising:

forming a first dielectric layer over an electrically conductive layer;

forming a phase change material layer over the first dielectric layer, the phase change material layer having a thickness gradient with different phase transition temperatures;

forming first and second electrically conductive contacts coupled to the phase change material layer, the phase change material layer having a first height value adjacent to the first electrically conductive contact, and a second height value adjacent to the second electrically conductive contact, the second height value being different than the first height value;

forming a graphene layer over the phase change material layer and having a perforated pattern therein; and

coupling circuitry to

apply a bias voltage between the first and second electrically conductive contacts, and

detect a sensing current in the phase change material layer caused by IR radiation received by the graphene layer, the IR radiation having a frequency range based upon the bias voltage.

18 . The method of claim 17 wherein the perforated pattern comprises an array of elliptical holes.

19 . The method of claim 17 wherein the phase change material layer comprises vanadium oxide.

20 . The method of claim 17 further comprising:

forming a transparent electrically conductive layer over the phase change material layer;

forming a second dielectric layer over the phase change material layer; and

forming a protective layer over the graphene layer.

21 . The method of claim 20 wherein the first dielectric layer comprises a polymer layer; and wherein the second dielectric layer comprises silicon nitride.