Raman scattering characterization of Ga_1-xAl_xAs/GaAs heterojunctions: Epilayer and interface

Abstract

We have used Raman spectroscopy to characterize Ga1-xAl xAs/GaAs heterojunctions (x≊0.9) grown by liquid phase epitaxy. The GaAs substrate had a (100) surface and the Ga1-xAlxAs epilayer was about 5000 Å thick. Signals were observed from both the Ga1-xAlxAs epilayer and the GaAs substrate at the interface. Information about the quality of the epilayer can be gained from several aspects of the spectrum including linewidths, violations of polarization selection rules (e.g., observation of symmetry forbidden TO mode), and the amplitude of the disorder-activated LA mode (DALA). These results are correlated with the properties of the substrate and growth condition. In addition the signal observed from the GaAs substrate revealed interesting features such as coupled plasmon modes and hence yielded information about band- bending and dopant diffusion at the interface.