Direct observation of nitrogen location in molecular beam epitaxy grown nitrogen-doped ZnO.
ZnO is a wide band gap, naturally n-type semiconductor with great promise for optoelectronic applications; the main obstacle yet to be overcome is p-type doping. Nitrogen, the most promising candidate currently being pursued as a dopant, has been predicted to preferentially incorporate into the ZnO lattice in the form of a N-2 molecule at an O site when a plasma source is used, leading to compensation rather than p-type doping. We demonstrate this to be incorrect by using N K-edge x-ray absorption spectra and comparing them with first-principles calculations showing that nitrogen, in fact, incorporates substitutionally at O sites where it is expected to act as an acceptor. We also detect the formation of molecular nitrogen upon annealing. These results suggest that effective p-type doping of ZnO with N may be possible only for low-temperature growth processes.
National Institute of Advanced Industrial Science & Technology, Tsukuba Central 4, Higashi 1-1-1, Tsukuba, Ibaraki, 305-8562, Japan. paul-fons@aist.go.jp
Paul
P
Fons
Hiroshi
H
Tampo
Alexander V
AV
Kolobov
Masataka
M
Ohkubo
Shigeru
S
Niki
Junji
J
Tominaga
Roberta
R
Carboni
Federico
F
Boscherini
Stephan
S
Friedrich