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

Electrical properties of ZnO crystals annealed at 600 degrees C in H-2, O-2, and Ar have been investigated. The two donors (D1 and D2) with the ionization energies of E-D1 similar to 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. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3565026]