An infrared external photoemissive detector can have an n-p heterojunction comprising an n-type semiconductor layer and a p-layer; the n-layer semiconductor comprising doped silicon embedded with nanoparticles forming Schottky barriers; and the p-layer is a p-type diamond film. The nanoparticles can be about 20 - 30 atomic percentage metal particles (such as silver) having an average particle size of about 5 - 10 nm. The p-layer can have a surface layer that has a negative electron affinity. The n-layer can be in the range of about 3 µm to 10 µm thick, and preferably about 3 µm thick. The doped silicon can be doped with elements selected from the list consisting of phosphorus and antimony.