Zinc oxide is a well-known wide bandgap semiconductor material. High exciton energy at room temperature makes it useful in optoelectronic applications. ZnO can be made available in bulk, film and nanostructured form as well. Nanostructures of ZnO have been proven to have augmented optical properties and extensively being used in optoelectronics and sensing applications. Here we have shown the effect of seed layer thickness on the chemical growth of ZnO nanorods. Two samples A and B has been prepared by hydrothermal bath synthesis having seed layer thicknesses of 120 nm and 350 nm, respectively. FEG-SEM images of nanorods revealed longer and high aspect ratio for sample B while sample A showed lower aspect ratio nanorods. XRD results indicate a dominant c-axis oriented (002) plane at around 33.5°. The calculated grain size of Sample A and B were 31.5 nm and 34.4 nm, respectively. Calculated strain values show a compressive strain in the crystal lattice. The Band edge PL peak emission for sample A and B was found to be at 368.74 nm and 368.38 nm at 18 K.
ZnMgO is extensively being used in UV based optoelectronic applications owing to its high bandgap and excitonic emissions at room temperature. In many applications, UV-Vis detection is required such as spectroscopy, medical applications and plasmonics. ZnMgO film and silicon can work in parallel to give a broad UV-Vis response. We fabricated ZnMgO/Si UV-Vis photo detector. UV-Ozone annealing can be used to increase the responsivity due to an increase in photoconductive gain. Here in this report, we have shown the effect of UV-Ozone on the transient behavior of the photodetector. The calculated responsivity values for 300 nm, 400 nm and white light were 3 A/W, 95 A/W and 50 A/W respectively. After UV-Ozone corresponding responsivity increased to 5 A/W, 180 A/W and 105 A/W respectively. The transient response of the photodetector was measured for asfabricated and UV-Ozone annealing. The transient behavior was fitted into two time constant of rise and fall time and switching parameters at 300 nm, 400 nm and white light are compared. The lesser time constant indicates carrier generation and recombination and the larger time constant is related with traps capture and release process. Rise time for 300 nm, 400 nm and white light was estimated to be 100, 10 and 8 ms respectively and the corresponding fall times were 140, 45 and 40 ms. Rise time for 300 nm illumination decreased from 100 to 70 ms after UV-Ozone.