Fe doping can be reckoned as a effective mean for attaning high resistivity GaN epitaxial material provided there is good lattice matching. Otherwise, it may cause deterioration of the GaN material surface topography, thereby degrading the electrical properties of two dimensional electron gas (2DEG) in HEMT device. Apart from this, Fe doping increases the trap at GaN buffer. Fe-GaN has potential for high power and high frequency transistors.

Thank you Dr. Rajib Biswas

Could you elaborate on screen the polarization field ?

There is a good chance that Fe doping in GaN changes the polarization. Fe has some unpaired electrons and when doped in GaN, these unpaired electrons due to their own spin polarization could affect the polarization of the waves (of specific wavelengths) passing through it.