Effects in the Optical and Structural Properties Caused by Mg or Zn Doping of GaN Films Grown via Radio-Frequency Magnetron Sputtering Using Laboratory-Prepared Targets

Abstract

GaN films doped with Mg or Zn were obtained via radio-frequency magnetron sputtering on silicon substrates at room temperature and used laboratory-prepared targets with Mg-doped or Zn-doped GaN powders. X-ray diffraction patterns showed broadening peaks, which could have been related to the appearance of nano-crystallites with an average of 7 nm. Scanning electron microscopy and transmission electron microscopy showed good adherence to silicon non-native substrate, as well as homogeneity, with a grain size average of 0.14 µm, and 0.16 µm for the GaN films doped with Zn or Mg, respectively. X-ray photo-electron spectroscopy demonstrated the presence of a very small amount of magnesium (2.10 mol%), and zinc (1.15 mol%) with binding energies of 1303.18, and 1024.76 eV, respectively. Photoluminescence spectrum for the Zn-doped GaN films had an emission range from 2.89 to 3.0 eV (429.23–413.50 nm), while Mg-doped GaN films had an energy emission in a blue-violet band with a range from 2.80 to 3.16 eV (443.03–392.56 nm). Raman spectra showed the classical vibration modes A1(TO), E1(TO), and E2(High) for the hexagonal structure of GaN.

Reactive plasma sputtering deposition of polycrystalline GaN thin films on silicon substrates at room temperature

“…The high-resolution TEM (HR-TEM) images in Figure 7.C-D were obtained after tilting a flake in the microscope so that its growth axis is in the plane. In this geometric configuration, some grains were in a [11][12][13][14][15][16][17][18][19][20] zone axis (Figure 7.D-E), which allows one to directly see the stacking of the GaN (0002) compact planes oriented perpendicular to the growth direction. To confirm this texture effect on a larger scale, selected area diffraction patterns were recorded, as shown in Figure 8.…”