Photocathode including nanostructures for extended wavelengths
A photocathode. The photocathode includes an absorber. The absorber a p-type bulk active layer and a plurality of nanostructures formed on the p-type bulk active layer. The Photocathode further includes the plurality of nanostructures, such that the plurality of nanostructures are formed at a band bending region between the bulk active layer and the vacuum.
1 . A photocathode epitaxial structure comprising:
a substrate material;
a p-type bulk active layer formed on the substrate material; and
a plurality of nanostructures formed between the substrate material and the p-type bulk active layer, positioned within a band bending region,
wherein the plurality of nanostructures comprise quantum-confined nanostructures including at least one of quantum wells or quantum dots, and wherein a total thickness of the plurality of nanostructures is less than a thickness of the band bending region.
2 . The photocathode epitaxial structure of claim 1 , wherein the plurality of nanostructures formed between the substrate material and the p-type bulk active layer comprises 2 to 5 nanostructure layers.
3 . The photocathode epitaxial structure of claim 1 , wherein the quantum wells comprise the plurality of nanostructures positioned within the band bending region.
4 . The photocathode epitaxial structure of claim 1 , wherein the quantum dots comprise the plurality of nanostructures positioned within the band bending region.
5 . The photocathode epitaxial structure of claim 1 , wherein the plurality of nanostructures formed between the substrate material and the p-type bulk active layer comprises one or more InGaAsNSb layers and one or more GaAsN layers.
6 . The photocathode epitaxial structure of claim 1 , wherein the plurality of nanostructures formed between the substrate material and the p-type bulk active layer comprises one or more InGaAs layers and one or more GaAsP layers.
7 . The photocathode epitaxial structure of claim 1 , further comprising an InGaP etch stop layer to prevent surface damage.
8 . The photocathode epitaxial structure of claim 1 , further comprising a window layer formed on the p-type bulk active layer.
9 . The photocathode epitaxial structure of claim 1 , wherein the p-type bulk active layer is doped exponentially by p-type impurities with levels of doping increasing away from an interface between the p-type bulk active layer and the substrate material.
10 . A photocathode comprising:
an absorber, the absorber comprising:
a p-type bulk active layer; and
a plurality of nanostructures formed on the p-type bulk active layer; and
wherein the plurality of nanostructures are exposed to a vacuum and are located within a band bending region between the bulk active layer and the vacuum, wherein the plurality of nanostructures are formed between a substrate material and the p-type bulk active layer in an epitaxial structure, and wherein, the plurality of nanostructures are proximate the vacuum.
11 . The photocathode of claim 10 , wherein the plurality of nanostructures comprise at least one of quantum wells or quantum dots located within the band bending region between the bulk active layer and the vacuum.