Contributions of $\hbox{N}^{+}$, $\hbox{N}_{2}^{+}$, $ \hbox{NO}^{+}$ Ion Implantation to p-Type Conversion of ZnO:Al Films

Different nitrogen sources, pure N
₂
, pure NO, and NO mixed with O
₂
(25% NO + 75% O
₂
), are used to confirm the effects of N
⁺
, N
₂
⁺
, and NO
⁺
ion implantation on the p-type conversion of ZnO:Al (AZO) films by plasma-immersion ion implantation (PIII) based on N-Al codoping mechanism. For the plasma of N
₂
, NO, and NO mixed with O
₂
, the major implanted ions are, respectively, N
₂
⁺
ions, N
₂
⁺
mixed with NO
⁺
ions, as well as N
⁺
mixed with O
⁺
ions, confirmed by the optical emission spectra of plasma. After activation by postimplanted annealing, the photoluminescence and X-ray photoelectron spectroscopy analyses indicate that the implanted N
⁺
, N
₂
⁺
, and NO
⁺
ions replace the O sites and form nitrogen atom substitutions at O sites [(N
_O
)], nitrogen molecule substitutions at O sites [(N
₂
)
_O
], as well as zinc nitrite and zinc nitrate, respectively. Among all the N-induced defects, only N
_O
contribute to the p-type conversion of ZnO films. That explains why p-type conversion is only successfully achieved by NO mixed with O
₂
, while others still remain n-type conductivity. The mechanism of p-type conversion by N
₂
, NO, and NO mixed O
₂
PIII was investigated in this paper.