Structural characterization of H plasma-doped ZnO single crystals by Hall measurements and photoluminescence studies

Nominally undoped, hydrothermally grown ZnO single crystals have been investigated prior to and after doping in remote H plasma. Characterizations have been made by temperature-dependent Hall effect (TDH) and low temperature photoluminescence (PL) measurements. The H content before and after the doping has been de-termined using nuclear reaction analysis and is compared to the density of shallow donors derived from the TDH measurements.
The electrical properties of the as-grown ZnO sin-gle crystals are found to differ significantly. This is as-cribed to the density ratio of shallow donors and compen-sating acceptors. PL measurements showed that AlZn, GaZn, and interstitial zinc (Zni) are prominent shallow donors in the as-grown samples.
Remote H plasma treatment produced a metallic conducting near-surface layer thus masking the electrical properties of the bulk. The electrical properties of the in-vestigated samples are very similar after the treatment, independent of the as-grown state, because the density of shallow donors far exceeds that of compensating accep-tors in the affected near-surface region. The maximum of the broad near-band-edge emission is found to be located at 3.3595 eV due to the high doping density.