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

Abstract

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, have been fabricated. A comprehensive characterization of the spectral response is developed in each case. Performances, specifications, and advantages of each kind of device are detailed, p-i-n ZnBeSe-ZnMgBeSe photodiodes exhibit a high responsivity (0.17 A/W at 150 nm) and a high rejection rate (10/sup 4/). Losses by recombination in the top p-type layer and p-type doping limitations lead to a decrease of the high energy response which is their major drawback. Thanks to the position of their depleted region on top of the structure. Schottky barriers and MSM photodetectors are much more suited for UV detection. With Schottky diodes, high efficiencies are obtained over the whole UV-A and -B ranges. Detectivity values above 10/sup 11/ mHz/sup 1/2/ W/sup -1/ have been measured. MSM detectors appear as an attractive alternative to Schottky barrier diodes with as high a response and nearly as low noise levels. This study thus demonstrates the potential of ZnSe- and ZnMgBeSe-based Schottky barriers and MSM devices for efficient detection in the UV region.