Photoluminescence and photoluminescence excitation of 0.635-eV EL0 emission in oxygen-doped semi-insulating GaAs.

The 0.635-eV photoluminescence emission present in oxygen-doped semi-insulating GaAs was studied with respect to temperature variation and photoluminescence excitation. The photoluminescence characteristics of the 0.635-eV emission are distinctly different compared to those of 0.68-eV EL2 emission. The radiative mechanism is explained well by the configuration coordinate model, which involves a complex center involving the deep oxygen donor on an arsenic site and a gallium vacancy as a nearest neighbor. The Frank-Condon shift and vibration energy of the excited state of the center were determined to be 0.16 and 0.025 eV, respectively.