Abstract
The active layer material quality and doping profile effects on the ZnO-based thin film metal-semiconductor-metal photodiode's (MSM-PD) performance are studied using a 2-D numerical simulation. The results of the simulation reveal that the temporal response advantages of increasing the doping concentration of the PD's active layer are only appreciable at low bias. Whereas, using the downgraded material, the temporal response advantages are maintained for all applied biases but at the expense of a very low responsivity. This paper discusses the possibility of improving the temporal response while maintaining excellent responsivity. It is shown that the composed structure, made of a good material heavily doped top layer and a bottom layer lightly doped made of downgrade material, exhibits the desired temporal response advantages while maintaining an excellent responsivity.