Calculation of linear and second-order optical response in wurtzite GaN and AlN

Abstract

We calculate the linear and nonlinear optical response of GaN and AlN in the wurtzite structure. The dielectric function ⑀(), the second harmonic generation susceptibility (2) (Ϫ2;,), and the linear electro-optic susceptibility (2) (Ϫ;,0) are all evaluated over a broad frequency range. These results are based on a first principles electronic structure calculation using the full-potential linearized augmented planewave method within the local density approximation. Corrections to the underestimation of the band gaps are included at the level of the scissors approximation, which is carefully incorporated within our susceptibility formalism. All independent components for the response functions are calculated; the results for GaN and AlN are very different, and those of AlN are in strong disagreement with predictions of the bond charge model. Results for all response functions at zero frequency are underestimated with respect to the available experimental values. A comparison of the calculated response functions for nonzero frequencies is made with the limited experimental data. We confirm both analytically and numerically that the calculated second-order susceptibilities obey various symmetry constraints below the band gap. ͓S0163-1829͑97͒04019-8͔

Ultrafast second-harmonic generation spectroscopy of GaN thin films on sapphire

“…1 In order to extract xzx (2) and zxx (2) from the measurements, we developed an analysis that incorporates the interference effects that arise in SHG spectroscopy of thin films with ultrafast light pulses. We find the variation of these nonlinear susceptibilities to be independent of the concentration of defect states associated with yellow band luminescence.…”

Band Structure and Optical Response in Ga x Al 1—x N

“…It can be seen a slight break in the wurtzite symmetry which in our opinion reflects the appearance of a slight structural modulation. We observe also an essential deviation in the behaviour of the subbands both for the particular pure GaN and GaAl compounds [4]. Drastical changes are observed for G±K±M 416 M. Malachowski, I. R. Kityk, and B. Sahraoui Coming out from the calculated energy band structure we have carried out the calculation of the imaginary part of the dielectric susceptibility using the tetrahedra method described in [16].…”

Nonlinear Optical Characterization of GaN Layers Grown by MOCVD on Sapphire

“…One can notice that for an ideal wurzite structure, the nonzero elements of the second-order nonlinear susceptibility tensor are related to each other as d 15 ≈ d 31 and d 33 /d 31 ≈ -2 [7,8].…”