MOCVD growth of monomethylhydrazine-doped ZnO layers

Nitrogen (N)-doped ZnO layers were grown using diethylzinc (DEZ), water (H2O) and monomethylhydrazine (MMHy) as Zn, O and N precursors, respectively. Raman spectra revealed N-related vibrational modes at 275, 510, 582 and 643 cm(-1) in addition to the host phonons of ZnO. The intensity of these additional modes was increased with increasing the amount of MMHy. These ZnO samples were thermally annealed under an oxygen ambient to activate N as an acceptor. By increasing the annealing temperature, the intensity of additional modes was decreased, which indicates the dissociation and re-evaporation of N complexes. By capacitance-voltage (C-V) measurements, it was observed that the capacitance was increased by increasing the positive bias voltage for N-doped as-grown ZnO layer, which indicates that this layer is n-type with donor concentration of 1 x 10(16) cm(-3). In contrast, the capacitance was decreased by increasing the positive bias voltage for N-doped ZnO layer annealed at 800degreesC. In addition, the neutral acceptor-bound exciton (A(0)X) emission and donor-acceptor pair (DAP) emission were observed in N-doped ZnO layer annealed above 800degreesC by low-temperature photolumineseence (PL) measurements. (C) 2004 Elsevier B.V. All rights reserved.