Effect of N and Al-N dual doping on optical, photoluminescence and transport properties of ZnO films

N-doped and Al-N dual-doped ZnO thin films have been synthesized on glass substrate by low-cost spray pyrolysis technique. Introduction of N and Al in ZnO affects the surface morphology and electro-optical properties of ZnO. SEM micrographs clearly show the formation of nano-scale semi-spherical and hexagonal crystalline grains. 3D AFM images revealed the formation of crystalline grains with array structure. Transparency of the films increased substantially for N and Al-N dual-doping in ZnO lattice in the measured optical spectrum range (380 to 1000 nm). Optical band gap calculations reveal that the un-doped, N-doped and Al-N dual-doped ZnO thin films are direct band gap semiconductors. The carrier concentration of undoped and Al-N dual-doped ZnO samples is found to be in the order of ~1015 cm−3. Highly N (>6%) doped ZnO samples shows p-type behavior. Photoluminescence study confirms both near band edge (NBE) and the deep level (DLE) emissions.