Photodetector

1. An UV photodetector comprising:

a substrate;

a template layer formed on the substrate;

an intrinsic AlGaN layer formed on the template layer;

a first n-type AlGaN layer and a second n-type AlGaN layer formed on the intrinsic AlGaN layer side-by-side and separated by a gap, wherein the gap exposes the intrinsic AlGaN layer;

a p-type layer formed on the second n-type AlGaN layer;

an n-type ohmic contact formed on the first n-type AlGaN layer; and

a p-type ohmic contact formed on the p-type layer, wherein the p-type ohmic contact is positively biased against the n-type ohmic contact when in use.

2. The UV photodetector according to claim 1 , wherein an UV transparent dielectric layer is formed on the intrinsic AlGaN layer in the gap.

3. The UV photodetector according to claim 1 , wherein each of the template, the first n-type AlGaN layer, the second n-type AlGaN layer and the p-type layer is made of GaN, and an Al-content of the intrinsic AlGaN layer is in the range of 46% to 50%.

4. The UV photodetector according to claim 1 , wherein a Schottky contact is formed on the intrinsic AlGaN layer in the gap.

5. The UV photodetector according to claim 1 , wherein an insulating dielectric layer is formed on the intrinsic AlGaN layer in the gap, a metal layer is formed on the insulating dielectric layer, and the metal layer, the insulating dielectric layer and the intrinsic AlGaN layer form a metal-insulator-semiconductor (MIS) structure.

6. The UV photodetector according to claim 1 , wherein the gap has a zigzag shape and has a lateral dimension of 1-3 microns.

7. The UV photodetector according to claim 1 , wherein the substrate and the template layer are UV transparent.

8. The UV photodetector according to claim 1 , wherein a thickness of the intrinsic AlGaN layer is in the range of 200-400 nm.

9. The UV photodetector according to claim 1 , wherein the first n-type AlGaN layer and the second n-type AlGaN layer are doped with Si at a doping level in the range of 1.0×10 18 to 1.0×10 19 cm −3 , respectively, and an Al-content and a thickness of each of the first n-type AlGaN layer and the second n-type AlGaN layer are in the range of 50% to 70% and 100-400 nm, respectively.

10. The UV photodetector according to claim 1 , wherein the p-type layer includes a p-type AlGaN layer and p-type GaN layer, the p-type AlGaN layer and the p-type GaN layer are doped with Mg at a doping level in the range of 1.0-10.0×10 19 cm −3 , respectively, and each has a thickness in the range of 50-100 nm, an Al-content of the p-type AlGaN layer is in the range of 50%-70%.

11. An UV focal plan array (FPA) imaging device, comprising an array of the UV photodetectors according to claim 1 .

12. An UV photodetector comprising:

a substrate;

a template layer formed on the substrate;

an intrinsic AlGaN layer formed on the template layer;

a first n-type AlGaN layer and a second n-type AlGaN layer formed on the intrinsic AlGaN layer side-by-side and separated by a gap, wherein the gap exposes the intrinsic AlGaN layer;

a p-type layer formed on the second n-type AlGaN layer; and

a Schottky contact formed on the intrinsic AlGaN layer in the gap.

13. An UV photodetector comprising:

a substrate;

a template layer formed on the substrate;

an intrinsic AlGaN layer formed on the template layer;

a first n-type AlGaN layer and a second n-type AlGaN layer formed on the intrinsic AlGaN layer side-by-side and separated by a gap, wherein the gap exposes the intrinsic AlGaN layer;

a Schottky contact formed on the intrinsic AlGaN layer in the gap; and

a metal layer formed on the second n-type AlGaN layer forming a Schottky junction therebetween.

14. The UV photodetector according to claim 13 , wherein a p-type layer is formed on the second n-type AlGaN layer.