As-rich GaAs crystals: Temperature-dependent photoluminescence and defect-mediated emission

We present a comprehensive structural and optical investigation of arsenic-rich GaAs crystals grown by the liquid-encapsulated Czochralski (LEC) method. Energy-dispersive X-ray spectroscopy confirms an As-enriched stoichiometry (Ga/As ≈ 0.73), while X-ray diffraction reveals a well-defined zinc blende phase with a strong (400) preferred orientation and a lattice constant close to that of stoichiometric GaAs, indicating good crystalline quality. Temperature-dependent photoluminescence (33–300 K) exhibits intense near-band-edge and bound-exciton emissions at 33 K (∼1.521 eV), accompanied by additional low-energy emission bands. The temperature evolution of the band gap follows the Varshni relation, yielding Eg(0) ≈ 1.52 eV. Analysis of the thermal quenching behavior of the integrated near-band-edge emission intensity using the Arrhenius model provides an activation energy of approximately 30 meV, suggesting that shallow non-radiative recombination centers dominate the deactivation process. These findings elucidate the role of excess arsenic in modifying defect-related recombination processes and radiative dynamics of GaAs and offer valuable insights for the design of defect-engineered optoelectronic and photonic devices.