| Summary: | In this paper, microwave (MW) activation of
sol-gel spin coated magnesium (Mg) doped gallium
nitride (GaN) thin films grown on sapphire (001)
substrates were reported. The attention was paid to the
effects of MW activation power on structural and optical
properties of these p-type GaN films. X-ray diffraction
results indicate that the Mg-doped GaN thin films exhibit
hexagonal wurtzite structure with (002) preferential
orientation. Besides, the Mg-doped GaN thin film
activated at 450 W has the highest dislocation density, 6, implies that it has the largest amount of nitrogen
vacancies compared to all the other samples, and
consequently the poorest crystalline quality as proved by
the drastic decrease in intensities of the XRD peaks of
the film. Since nitrogen vacancies are favourably formed
only upon the removal of hydrogen from p-type GaN, it
can be deduced that the activation process of Mg
dopants is most efficient at 450 W. Tensile strain along caxis of the film activated at 450 W further validates this statement. Raman scattering measurements showed the
presence of E2(high) mode of hexagonal GaN in all the
Mg-doped GaN thin films, except in film activated at MW
power of 450 W where the E2(high) mode peak is
extremely weak and broad. The smallest crystall ite size
of the Mg-doped GaN thin film activated at MW power
of 450 W leads to optical phonon confinement, resulting
in broadening of E2(high) mode. In summary, 450 W is
the best power for the activation process of Mg dopant,
but yet it is not the most ideal MW power because it
deteriorates the crystalline qualit y of the films.
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