Photocurrent in MIS structures based on germanosilicate films

The photocurrent in metal-insulator-semiconductor (MIS) structures based on germanosilicate films on n-type silicon with a transparent top electrode made of indium tin oxide has been studied. The first structure contained a GeO[SiO₂] layer as a dielectric, and the second structure contained an additional Ge layer 3 nm thick, separated from the silicon substrate by a tunnel-thin layer of SiO₂. High photosensitivity was obtained for both structures, both as-deposited and after annealing at 500 °C for 30 minutes. A mechanism for the generation of photocurrent is proposed, based on the absorption of photons in a depletion region of silicon and tunneling of charge carriers through the dielectric. In the case of the second structure, an additional mechanism for the occurrence of photocurrent associated with the absorption of photons in the Ge layer is assumed. The studied MIS structures can be used in simple, inexpensive photodiodes that do not require the creation of p–n junctions.