The enhanced photodetector was fabricated on silicon-on-insulator substrates consisting of a 3-μm SiO₂ layer and a 1.5-μm Si device layer. On top of that, an 80-nm PbSe thin film was deposited by an evaporation process. Hole arrays arranged in a square lattice were formed by ion etching. The depth of the holes was 150 nm. The Chinese scientists fabricated three devices: one without hole arrays and two with holes, with diameter (d)/lattice period (p) values of 700/1,000 nm and 700/2,333 nm, respectively. Two separate sets of Au metal fingers were placed on the top layer as an interdigital electrode to generate an electric field in the PbSe thin film. The team measured and compared the detection performance of all three devices at different wavelengths.

The researchers found that, in agreement with numerical simulations based on a finite-difference time-domain method, the peak absorption wavelength of the photodetector increases as the lattice period increases. High absorption exceeding 90% was achieved at 850 nm, 1,064 nm, 1,310 nm, and 1,550 nm when the lattice period was 1,000 nm, 1,280 nm, and 1,520 nm, respectively.