Postdeposition thermal annealing influence on the activation of the cosputtered AlN-ZnO films

Cosputtered aluminum nitride-zinc oxide (AlN-ZnO) films at a theoretical atomic ratio of 10% [Al / (Al + Zn) at.%] were postannealed at 450°C for 30 min under ambient nitrogen and vacuum, respectively. The activated impurities in these annealed samples were investigated through the room-temperature (RT) and low-temperature (LT) photoluminescence (PL) spectra as well as their temperature-dependent Hall-effect measurements. It was found that the donor-acceptor-pair (DAP) emission related to V_Zn-Al_Zn transition at 2.86 eV predominated over the defect-transition luminescence in the RTPL spectrum of the vacuum-annealed sample, for which possessed a high electron carrier concentration. With the help of the temperature-dependent Hall measurement, the shallow donor level corresponded to Al on Zn site (Al _Zn) was derived as E_C-(51±4) meV. By contrast, the RTPL spectrum of the nitrogen-annealed AlN-ZnO cosputtered film, showing p-type conduction with a hole concentration of 10¹⁸ cm^-3, was dominated by the V_O-N_O deep level emission approximately at 1.87 eV. The estimated acceptor level corresponded to the N on O site (N _O) was E_V+ (149±6) meV. The binding energy and activation energy associated with the N_O acceptor were also determined by the LTPL and temperature-dependent PL spectra.