Optical analysis of tin-doped GaNAs layers grown on GaAs by molecular beam epitaxy

The optical non-destructive characterization of tin-doped GaNxAs1-x layer grown on GaAs (100) is presented. Molecular beam epitaxy was employed to grow GaNAs:Sn samples with nitrogen molar content at two different values, x similar to 0.001 and similar to 0.02. The n-type doping concentration was controlled by the Sn effusion cell temperature (T-Sn), exploring the range from 700 to 850 degrees C. High-resolution x-ray diffraction rocking curves of the samples indicate that it is possible to obtain GaNAs:Sn layers with appropriated crystallinity. Raman spectra present modifications in vibrational modes related to the Sn atom incorporation. The plasmon-phonon-coupled mode frequency and intensity are evaluated, showing a T-Sn-dependent donor atom concentration range from 10(16) to 10(19) cm(-3). Spectral signatures obtained by photoreflectance spectroscopy reveal an increasing E- broadening parameter as the Sn effusion cell temperature is raised. Additionally, from Franz-Keldysh oscillations it is observed that the internal electric field strength increases with the donor concentration. The optical results were contrasted using the four-point probe method, demonstrating changes in sheet resistivity for the samples according with the employed spectroscopies. For similar T-Sn, the set of samples with x similar to 0.02 shows increased properties related to tin incorporation for each characterization technique.

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