Effect of annealing on the electrical properties of ZnO crystals grown by chemical vapor transport

Electrical properties of ZnO crystals annealed at 600 °C in H 2, O 2, and Ar have been investigated. The two donors (D1 and D2) with the ionization energies of E D1 ∼0.043 eV and E D2 =0.08 eV and a compensating acceptor were observed in the as-grown and annealed samples. There was no significant change in electrical properties of the sample annealed in H 2, while annealing in O 2 and Ar affected the electron concentration. The decrease of the D1 donor concentration and the increase of the compensating acceptor concentration were observed in the samples annealed in O 2. The electron mobility for the sample annealed in O 2 decreased because of the increase of the compensating acceptor concentration