Effect of doping concentration on optical and electrical properties of intrinsic n-type ZnO (i-ZnO) and (Cu, Na and K) doped p-type ZnO thin films grown by chemical bath deposition method

Pure ZnO and copper (IB group), sodium (IA group) and potassium (IA group) and doped ZnO thin films on glass substrate by chemical bath deposition method have been studied for Hall effect measurements, resistivity, Raman and photoluminescence (PL). The influence of dopant content on carrier concentration, electrical resistivity, and Hall mobility of the thin films are analyzed. Electrical conductivity measurements of ZnO are carried out by two probe method and activation energy for the electrical conductivity of pure and doped ZnO is found out. The Raman scattering of the pure ZnO and doped ZnO shows the first and second orders of polar and non-polar modes. Raman spectra confirms the hexagonal wurtzite structure of pure and doped ZnO with E$_{2}$ (high) mode at 439 cm$^{-1}$ and presence of other possible defects. Photoluminescence (PL) at room temperature results indicate the emission occurs at close band lines and the outcomes are identified with a few inherent imperfections in the doped ZnO thin films. The PL results demonstrate the upgraded optoelectronic properties, specifically, the carriers for long life span is executed by the oxygen opportunities. Raman spectroscopy and photoluminescence confirm existence of zinc interstitials (Zni) as well as oxygen vacancies (Vo). Resistivity as low as 15 $\Omega$-cm, Hall mobility as high as 6.2 cm$^{2}$/Vs and effective carrier concentration as high as 1.70$\times$ 10$^{17}$e$^{-}$/cm$^{3}$ have been obtained.