Defects in Compound Semiconductors Caused by Molecular Nitrogen

The interaction of nitrogen molecules (N-2) with the host lattice of compound semiconductors is investigated using first-principles density-functional calculations. In ZnO it is found that N-2 causes localized states in the band gap either by forming an N2O molecule or by breaking a Zn-O bond. This mechanism contributes to the observed low nitrogen doping efficiency in ZnO. The appearance of localized states caused by N-2 was also found in other semiconductors such as MgO and NaCl.