The Investigation of Macroscopic Polarization in AlN, GaN and AlGaN Semiconductors and Aluminum Concentration Effect on Band Gap and Macroscopic Polarization in the AlxGa1-xN

In this research we studied the electronic – crystalline structure in the semiconductor compounds of gallium nitride, aluminum nitride and aluminum gallium nitride, those have spontaneous polarization in 0001 axis and good piezoelectric properties. We used the Wien2k package, which works based on the density functional theory and the Berry’s phase approach to investigate Structural parameters, band gap, Operating and intensity of polarization for aluminum nitride, gallium nitride and aluminum gallium nitride semiconductors. Also, we studied their interaction in replacement of aluminum cation in triple semiconductor of aluminum gallium nitride. The results of the calculations showed that the rate of spontaneous and piezoelectric polarization and total macroscopic polarization in nitride semiconductors is high. We used two concentrations of aluminum as 12.5 and 37.5 percent in the ternary compound of AlxGa1-xN to calculate the polarization. Moreover, our calculations showed, that when the amount of aluminum cations increases, the polarization increases too. We also found that a higher share of the macroscopic polarization is attributed to the spontaneous polarization. In addition to, the spontaneous polarization in this case has a non-linear and quadratic relationship with concentration. Moreover, our calculations for band gap of compounds showed that in all of them the band gap is on Γ axis and straight, when the amount of aluminum cations decreases in AlxGa1-xN, the band gap energy decreases too.