Radiation-induced defect evolution in GaAs(O):Cr studied by Raman, FTIR and Hall measurements

In this work, the effect of high-fluence electron irradiation (4 × 10 17 , 5 × 10 17 and 6 × 10 17 e/cm 2 ) on GaAs(O):Cr crystals is systematically investigated using Raman and infrared (FTIR) spectroscopy in combination with Hall effect measurements. The analysis is focused on radiation-induced defect evolution and its impact on structural and transport properties. Raman spectroscopy reveals a systematic shift of the transverse optical (TO) phonon mode toward higher wavenumbers with increasing fluence, corresponding to a transition from tensile to compressive strain. The stress changes from δ ≈ +0.5 GPa to δ ≈ −0.55 GPa, while the strain evolves from ε ≈ +0.004 to ε ≈ −0.004, suggesting the development of compressive lattice distortion, which may be associated with radiation-induced defect redistribution and local lattice reorganization. FTIR spectra demonstrate a non-monotonic evolution of absorption bands. A pronounced modification is observed in the high-frequency region (∼900–960 cm −1 ), where the initially asymmetric band near ∼946 cm −1 evolves into two distinct components at higher fluences, indicating the formation of different Cr–O defect configurations and increased local ordering. Hall measurements reveal temperature-dependent changes in carrier concentration and transport properties after electron irradiation. At the highest fluence, the mobility reaches ∼179 cm 2 /V·s at 100 K and ∼65 cm 2 /V·s at 300 K, while the resistivity remains within ∼(2.95–3.58)×10 −1 Ω cm, indicating enhanced compensation and defect-controlled transport. The combined analysis reveals a close correlation between radiation-induced defect evolution, lattice strain, and charge transport. The experimental observations suggest that defect redistribution and local structural rearrangement become increasingly important at high irradiation fluences, thereby influencing the functional properties of GaAs(O):Cr under electron irradiation.

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