Estudo de filmes finos de GaAS (1-x) Nx/GaAS por espectroscopia Raman e de Fotoluminescência

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The dependence of nitrogen (N) concentration on optical properties in thermally treated and as grown thin films of GaAs1−xNx, with 0, 0144 x 0, 0370, is investigated through Raman spectroscopy and Photoluminescence. Raman spectra exhibits the presence of two GaAs1−xNx characteristic modes. A systematic decrease of the longitudinal optical GaAs-type phonon frequency (LO1) near 292 cm−1 and a linear increase of longitudinal optical phonon of the GaN-type (LO2), near 475 cm−1 is observed with increasing N concentration. It is also evident that the N concentration in GaAs1−xNx, determined by Raman spectroscopy (xRaman), exhibits a linear dependence with the one determined by High Resolution X-Ray Diffraction (HRXRD) (xXRD). It was verified that the systematic redshift observed for the LO1 phonon, usually associated to lattice strain and alloy effects, is associated with non-intentional doping and the loss of long range crystaline order. The photoluminescence (PL) results showed a reduction of up to 460 meV of the GaAs1−xNx band gap with increasing N concentration. PL measurements as a function of temperature and excitation intensity, revealed that the decrease of band gap energy with temperature increase is significantly greater for GaAs compared to GaAs1−xNx, and that at 7K the carrier bimolecular recombination process is predominantly radiative. All PL results are explained by the Band Anticrossing model.

ASSUNTO(S)

gaasn semicondutores raman stress fisica fotoluminecência

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