Realization of Na-doped p-type non-polar a-plane Zn1−xCdxO films by pulsed laser deposition

Na-doped non-polar Zn1−xCdxO thin films with different Cd content were grown on r-plane sapphire substrates by pulsed laser deposition. The Cd content in the Zn1−xCdxO thin films was adjusted via controlling substrate temperature. Based on the X-ray diffraction analysis, Na-doped Zn1−xCdxO films with Cd content below 5.3 at.% exhibit unique non-polar 〈112¯0〉 orientation, while the films with Cd content above 5.3 at.% present 〈0 0 0 1〉 and 〈112¯0〉 mixed orientations. With an effective incorporation of Na, Na-doped non-polar Zn1−xCdxO films exhibit p-type conductivity, as confirmed by rectification behavior of n-ZnO/p-Zn0.947Cd0.053O:Na homojunction. An optimized result with a resistivity of 67.43 Ω cm, Hall mobility of 0.28 cm2/V s, and hole concentration of 3.31 × 1017 cm−3 is achieved, and electrically stable over several months. The chemical states of Na were analyzed by X-ray photoelectron spectro scopy. Room-temperature photoluminescence measurements exhibit redshift of the near-band-edge emission by alloying Cd.