INVESTIGATION ON THE PROPERTIES OF ZnN THIN FILMS FABRICATED BY MAGNETRON SPUTTERING FROM ZnN TARGET FOR SOLAR CELL APPLICATIONS

摘要

Zinc nitride, ZnN, thin films were deposited by magnetron sputtering using, for the first time, ZnN target, in plasma containing pure Ar and pure N_2 gases and their properties were examined with annealing in flowing nitrogen. The rf-power was 100W and the total pressure was 5mTorr. ZnN thin films deposited in Ar plasma were n-type, exhibited low resistivity (4×10~(-2)Ωcm), high carrier concentration (3×10~(20)cm~(-3)) and very low transmittance due to excess Zn in their structure. After annealing at 300℃, most of the Zn in the structure was converted into stoichiometric zinc nitride, Zn_3N_2. The films became more transparent (> 80%) with a shoulder in transmittance at around 365nm, their electrical properties were improved (resistivity 3×10~(-3)Ωcm and carrier concentration 6×10~(21)cm~(-3) . Further annealing up to 550℃ decreased conductivity and carriers concentration. Low temperature photoluminescence revealed band-edge emission peaks. ZnN films deposited in N_2 plasma were stoichiometric Zn_3N_2 with high resistivity and high transmittance. These films also exhibited the shoulder in transmittance at 360nm, but there was no change in their properties with annealing. Zinc nitride has been found to be a wide band gap material, with high transmittance and electrical properties which can be tuned with annealing.