Defects in Compound Semiconductors Caused by Molecular Nitrogen

The interaction of nitrogen molecules (N2) with the host lattice of compound semiconductors is investigated using first-principles density-functional calculations. In ZnO it is found that N2 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 N2 was also found in other semiconductors such as MgO and NaCl.