Improvement of electrical stability of polycrystalline ZnO thin films via intentional post-deposition hydrogen doping

We investigate the hydrogen doping effect on polycrystalline ZnO thin films prepared by the photoassisted metalorganic chemical vapor deposition technique. In situ post-deposition hydrogen doping was performed using mercury-sensitized photodecomposition of hydrogen gas. From Fourier transform infrared spectra, we observe small changes in O-H bond-stretching local vibrational modes as a result of hydrogen doping. The photoluminescence measurements reveal that intentional hydrogen doping significantly suppresses nonradiative recombination centers in the ZnO films. The undoped ZnO film reveals a heavily n-type as-grown conductivity due to the high hydrogen content, but it is unstable in a humid air atmosphere. However, the electrical stability is significantly improved as a result of hydrogen doping.