Defects in crystalline materials can modify both their vibrational and electronic properties. In this work, these effects are studied through Raman and photoluminescence spectroscopies. The study focuses on high-electron-mobility III-V semiconductors with defects induced by proton irradiation. The samples were epitaxially grown in a MOVPE reactor at TU Berlin (Germany) and subsequently irradiated at the Tandem accelerator of CAB-CNEA (Bariloche, Argentina).

In this type of sample, defects are expected to deteriorate crystal quality, which in turn should reduce electron mobility and degrade the phonon spectrum. However, spectroscopic studies revealed an improvement in the features of the Raman peaks associated with LO phonons: their intensity increases and their width narrows in the more defective regions, contrary to expectations. Photoluminescence results, on the other hand, behave as expected: irradiated regions show a decrease in overall intensity, new peaks, and a flattened spectrum.

This work discusses the origin of the defect-dependent Raman intensity of LO phonons. For this purpose, studies were conducted on Raman scattering selection rules using polarizers, on the effective cross-section by varying the incident beam power, and on the resonance response by tuning the incident wavelength.