First-principle Study Of Electronic And Optical Properties Of Wurtzite Structure GaN

We use first-principles density functional theory (DFT) of the generalized gradient approximation (GGA) plane wave pseudopotential method to calculate the electronic and optical properties of ideal GaN and Al/InGaN ternary solid solution compounds.The physical properties of GaN and it's research progress, as well as the basic theory of first-principles have been briefly introduced.We calculation the upper-valence bandwidth in a series of plane-wave cut-off energy. Based on the convergence of calculation results, we found that make 600eV as the plane-wave cut-off energy can completely describe the wave function. At this condition, we calculate the wurtzite GaN lattice constant, energy band structure, electronic density of states and dielectric function and so on. Through the GGA+PBE scheme, we obtain the lattice constants, which are good agreement with experimental values. However, using the GGA pseudopotential, the band gap of the calculated values are smaller than the experimental values.At last, the proportion of different components of Al, In have been added into wurtzite GaN to form a ternary solid solution compounds. We obtain the lattice constants a and c, partial coefficients, and bowing parameters of AlGaN and InGaN. Respectively, the partial coefficient of AlGaNδ_a andδ_c is 0.019±0.012? and 0.038±0.070?, bowing parameter is 0.693±0.250eV; the partial coefficient of InGaNδ_a andδ_c is -0.065±0.015? and 0.087±0.045?, bowing parameter is 4.283±0.689eV.The results show that Al components added into GaN can widen the optical band gap. With increasing of Al composition, the curves of optical absorption are gradually moving toward the high-energy area. In other hand, In components added into GaN can reduce the optical band gap. With increasing of In composition, the curves of optical absorption are gradually moving toward the low-energy area.Finally, we find that, AlGaN and InGaN ternary solid solution compounds have a good performance in the 5eV-10eV energy area. AlGaN has a better performance than InGaN, which also makes it as microwave devices and UV detector substrate material has a very good application prospects.