Temperature-dependent photoluminescence of ZnO films codoped with tellurium and nitrogen

The photoluminescence spectra as well as their temperature dependence of the tellurium and nitrogen (Te-N) codoped ZnO films have been investigated in detail. Explicit evidences of the emissions related to two acceptors [A ₁: the N_O-Zn-Te subunits and A₂: the conventional N ions substituting on oxygen sites (N_O)] have been found. The acceptor activation energy level of the A₁ (∼118-124 meV) is much shallower than that of the A₂ (∼224-225 meV) indicating that the A₁ should be mainly responsible for the room-temperature p-type nature of the codoped samples. Meanwhile, the acceptor activation energy level of A₁ shows a slight decrease (∼6 meV) as the Te atomic concentration increases in the codoped samples implying that the actual form of the A₁ may be a mixture of the N_O-Zn-nTe (n 1, 2, 3, 4). More incorporation of the Te ions into N-doped ZnO films not only makes the acceptor energy level shallower but also improves the crystalline quality and results in the efficiently suppressed native donorlike defects. The optical properties accord well with the crystalline and electrical ones indicating that the Te-N codoping technique is a potentially feasible route to get controllable p-type ZnO materials.