Gallium Nitride is a promising material for different applications due to its superior characteristics with respect to conventional semiconductors: wide band gap, low intrinsic carrier density, high electron mobility, high critical field, high thermal stability and high saturation velocity. Despite of these advantages, GaN materials also show negative aspects, such as the very high cost and the less effective growing methods. In fact, the different techniques used for the GaN epitaxial growth does not seem very simple due to the risk of obtaining undesired effects in the final structure. Valid examples can be the presence of non-intentional doping inside the material or the formation of dislocation layers, which produce worse electrical and optical properties that compromise the resulting structure.