Evaluation of the potential of ZnSe and Zn(Mg)BeSe compounds for ultraviolet photodetection

We report on blue-violet and ultraviolet (UV) light detectors based on ZnSe and Zn(Mg)BeSe compounds lattice matched onto GaAs substrates. Three types , namely p-i-n, Schottky, and metal-semiconductor-metal (MSM) structures, h ave been fabricated. A comprehensive characterization of the spectral respo nse is developed in each case. Performances, specifications, and advantages of each kind of device are detailed. P-i-n ZnBeSe-ZnMgBeSe photodiodes exh ibit a high responsivity (0.17 A/W at 450 nm) and a high rejection rate (10 (4)). Losses by recombination in the top p-type layer and p-type doping lim itations lead to a decrease of the high energy response which is their majo r drawback. Thanks to the position of their depleted region on top of the s tructure, Schottky barriers and MSM photodetectors are much more suited for UV detection. With Schottky diodes, high efficiencies are obtained over th e whole UV-A and -B ranges. Detectivity values above 10(11) mHz(1/2) W-1 ha ve been measured. MSM detectors appear as an attractive alternative to Scho ttky barrier diodes with as high a response and nearly as low noise levels. This study thus demonstrates the potential of ZnSe- and ZnMgBeSe-based Sch ottky barriers and MSM devices for efficient detection in the UV region.