Nitrogen doping and p-type conductivity of ZnO films grown by vapor phase epitaxy

The incorporation and electrical activity of nitrogen as an acceptor in ZnO has been investigated. Low temperature Metalorganic Vapor Phase Epitaxy (MOVPE) growth, using diallylamine as nitrogen precursor, yields to incorporation of nitrogen in the range 10 16 -10 21 cm -3 . The electrical activity of nitrogen is demonstrated through the increased compensation of the natural donors with doping level. Close Space Vapor transport (CSVT) and Chemical Vapor Transport (CVT) are found to be less efficient for nitrogen incorporation. This suggests that the use of high temperature growth is a limiting factor for nitrogen incorporation in ZnO. Ex-situ techniques have been tried for both electrical activation and nitrogen incorporation in ZnO. High pressure annealing under oxygen pressure shows a conversion to p-type on nitrogen doped samples grown by MOVPE. Finally, diffusion of nitrogen was carried out on undoped MOVPE layers under high pressure conditions stemming from the decomposition of NH 4 NO 3 . Conversion to p-type conductivity was observed in a systematic way with measured hole concentrations up to 6.5.10 17 cm -3 . These results suggest that ex-situ treatment can be a practical way to realize p-type ZnO layers.