Annealing effects on the p-type ZnO films fabricated on GaAs substrate by atmospheric pressure metal organic chemical vapor deposition

Research highlights: → Intrinsic ZnO film fabricated on semi-insulating GaAs substrate by AP-MOCVD: p-type conductivity with a hole concentration of 3.2 x 1018 cm-3. → ZnO/GaAs post-annealed at 500-600 deg. C: p-type conductivity with hole concentrations ranging from 4.7 x 1018 to 8.7 x 1019 cm-3. - Abstract: The effects of post-annealing conducted at 500-650 deg. C on structural, electrical and optical properties of ZnO film fabricated on GaAs (1 0 0) substrate by atmospheric pressure metal-organic chemical vapor deposition are investigated. X-ray diffraction analyses show that the Zn3As2 and ZnGa2O4 phases are produced for the specimens post-annealed at 500 deg. C and above. Hall measurements indicate that stable p-type ZnO films with hole concentration ranging from 4.7 x 1018 to 8.7 x 1019 cm-3 can be obtained by modulating the annealing temperature from 500 to 600 deg. C. In particular, room-temperature photoluminescence (PL) measurements indicate that the superior-quality p-type film could be achieved by a post-annealing treatment at 600 deg. C. Moreover, low temperature PL spectra at 10 K are dominated by the acceptor-related luminescence mechanisms for the films post-annealed at 550 deg. C and above. The ionization energy of acceptor was calculated to be 133-146 meV, which is in good agreement with that theoretically predicted for the AsZn-2VZn complex in ZnO. The interdiffused arsenic atoms in the film post-annealed at 600 deg. C are suggested to form the AsZn-2VZn complex quite effectively, resulting in the most enhanced p-type conductivity and improved material quality.