Hydrothermal ZnO; Mastering of Lithium content and formation of Palladium Schottky diodes

Abstract

In this thesis we have annealed hydrothermally (HT) grown ZnO samples at temperatures ranging from 600C to 1600C, and examined the effects on the lithium content, the resistivity and the surface topography. Starting with highly resistive samples, we managed to reduce both the Li concentration and the resistivity with four orders of magnitude each to 10^13 cm^-3 and <1ohm*cm, respectively. Our findings showed a correlation between the Li concentration and the resistivity, and also a polarity effect on the surface roughness resulting from, what we believe, is lithium (Li) diffusion.

We then tuned the resistivity and the surface roughness of some HT ZnO samples, before realizing palladium (Pd) Schottky diodes on the (000-1) O-face, resulting in diodes with following properties: current rectification of up to eight orders of magnitude from -2V to 2V, low series resistance of 20ohm, low ideality factor of 1.06, reverse current density of J(V=-2)=10^-7A/cm^2 and an effective donor concentration of mid-10^16cm-3. A surface polarity effect on the diode quality was also observed.