Laser annealing of laser assisted molecular beam deposited ZnO thin films with application to metal-semiconductor-metal photodetectors

We report on the effect of postdeposition laser annealing of undoped zinc oxide (ZnO) thin films grown by laser assisted molecular beam deposition. Hall-effect measurements show that some undoped ZnO films change from n type with mobility values in the range of 200 cm ² V ^-1 s ^-1 to p-type material with mobility value of 73 cm ² V ^-11 s ^-1, after laser annealing. The photoconductive behavior was clearly seen on the laser-annealed samples, with values of 0.28 mΩ ^-1. The structural and optical properties of the films were improved with laser annealing as shown by scanning electron microscopy, x-ray photoelectron spectroscopy analysis, and photoluminescence measurement. All of the nonlaser and laser annealed samples showed near-band emission at ∼3.3 eV. Metal-semiconductor-metal photodetectors were fabricated from the films.