## 3 Results and Discussion
### Electron Microscopy, Profimometry and Resistivity  
Figure 3 shows the superficial morphology for the Zn-doped GaN films (Figure 3a), and Mg-doped GaN films (Figure 3b). SEM micrographs of the grown films by radio-frequency magnetron sputtering demonstrated good adherence to the substrate, as well as homogeneity. Figure 3a showed an irregular grain surface with a grain size average of 0.14 \(\upmu\)m. Figure 3b also demonstrated an irregular grain surface with a grain size average of 0.16 \(\upmu\)m, where the irregular grains could be formed by a crystallite agglomerate with a size average of 7 nm, as can be calculated from the XRD analysis using the ICDD PDF-4-2018 software and the Debye-Scherrer equation. Mg- or Zn-doped GaN films, grown by sputtering using laboratory-prepared targets of Mg- and Zn-doped GaN powders, had a better adherence and homogeneity compared to grown films obtained via nitridation of GaAs substrates or MOCVD [18]. EDS elemental analysis corresponding to Figure 3a,b is shown in Figure 3c,d, respectively. These spectra only demonstrated an elemental contribution of gallium, nitrogen, and a small elemental contribution of oxygen in the Mg- or Zn-doped GaN films. It is important to mention that the residual oxygen's non-intentional impurity might be related to the hysteresis effect, which can occur in the early stages of the sputtering deposition due to system instability. This residual oxygen could affect the optical properties of the GaN films, producing emission peaks in the red luminescence  
Figure 2: (a) X-ray diffraction pattern of the Mg-doped GaN films; (b) X-ray diffraction pattern of the Zn-doped GaN films; (c) ICDD card: 00-050-0792 for hexagonal GaN. (RL). EDS spectra did not show the presence of the incorporation of magnesium or zinc, which could be due to its small atomic percentage (1.0 mol %), compared to other elements. Additionally, the overall accuracy of the equipment used was approximately 1 weight percent (wt%) with a sensitivity of approximately 0.1 weight percent (wt%) [17,19]. EDS elemental analysis does not show the contributions of other impurity atoms such as carbon, or silicon belonging to the substrate. Figure 4 shows the X-ray photo-electron spectroscopy (XPS) of the Mg- or Zn-doped GaN films. Both samples showed similar behavior in the peaks for high energies of Ga 2P\({}_{3/2}\) and Ga 2P\({}_{1/2}\) with respective values of 1117.75 and 1144.61 eV, which has a difference of 1.35, and 1.41 eV for the L\({}_{2}\), and L\({}_{3}\) levels of the element in its natural form, respectively (Figure 4a). The atomic percentage for Ga 2P was approximately 51.7%. Additionally, the energy peak related to N 1s in both samples was obtained at 398.43 eV for the K level (Figure 4b), with an atomic percentage of 31.1%. This characterization technique showed the presence of a very small amount of magnesium (2.10 mol%), and zinc (1.15 mol%) for the two film types, which could indicate the incorporation of magnesium or zinc into GaN films. Figure 4c shows the Mg 1s peak, with a binding energy of 1303.18 eV, and an energy difference of 0.18 eV for the K level of the element in its natural form. Figure 4d, shows the Zn 2P\({}_{3/2}\) peak with a binding energy of 1024.76 eV, and a difference of 2.96 eV for the L\({}_{3}\) level, which might be related to the Zn incorporation into GaN. The electron density decreasing the base element (Ga), shifts the peak positively. The oxygen non-intentional impurity showed a peak for O 1s, which corresponded to K level, and had a binding energy of 531.54 eV, and an atomic percentage of 13.9% (Figure 4e). Figure 3: (**a–c**) SEM-EDS micrographs for the Zn-doped GaN films; (**b–d**) SEM-EDS micrographs for the Mg-doped GaN films. Figure 5 shows the transmission electron microscopy micrograph (TEM) for the Zn-doped GaN films. Figure 5a, shows uniform growth with an interplanar spacing of 2.59 A (a picture of the interplanar spacing measurement is shown in the Figure 5 box).