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

The optical non-destructive characterization of tin-doped GaN x As 1−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 ~ 0.001 and ~ 0.02. The n-type doping concentration was controlled by the Sn effusion cell temperature ( T Sn ), exploring the range from 700 to 850 °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 ~ 0.02 shows increased properties related to tin incorporation for each characterization technique.