Two-photon absorption in GaN, GaInN, and GaAlN alloys

We have carried out full band-structure-based studies of two-photon absorpt ion coefficients in the GaN compound, and GaInN and GaAlN alloys. An accura te Hamiltonian and resulting wave functions and band structures are used in the calculations. The coefficients in GaN calculated without any adjustabl e parameters agree very well with recent experiments. We further show that the two-photon absorption coefficients can be increased or decreased by add ing In or Al to the GaN compound. The spectral variation of the absorption coefficient can be explained in terms of the alloy-induced changes in the b and gap and joint density of states. (C) 2000 American Institute of Physics . [S0003-6951(00)04129-2].