Effects of annealing ZnO in hydrogen, oxygen, and argon have been investigated using deep level
transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS) measurements. Current-voltage (IV)
measurements indicate a decrease in zero–bias barrier height for all the annealed samples.
Conventional DLTS measurements reveal the presence of three prominent peaks in the un-annealed
and annealed samples. A new peak with an activation enthalpy of 0.60 eV has been observed in the H2
annealed samples, while an estimated energy level of 0.67 eV has been observed in Ar annealed
samples. O2 annealing does not introduce new peaks but causes a decrease in the concentration of the E3
peak and an increase in concentration of the E1 peak. The concentrations of all the intrinsic defects have
decreased after H2 and Ar annealing; with Ar annealing giving peaks with the lowest concentrations.
The E2 peak anneals out after annealing ZnO in Ar and H2 at 300 C. From the annealing behaviour of
E3, we have attributed to transition metal ion related defects, while E4 has been explained as a defect,
whose formation favours oxygen deficient conditions. Laplace DLTS has successfully been employed to
resolve the closely spaced energy levels in the E4 peak, splitting it into three peaks with energy levels,
0.68 eV, 0.58 eV, and 0.50 eV below the minimum of the conduction band for the Ar annealed sample.