Photoluminescence enhancement monitored in real time during photowashing of GaAs

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Abstract
We have observed the luminescence emitted from GaAs during the surface treatment process known as photowashing. This allows us to probe the extent of surface quality improvement in real time as the treatment proceeds. We observe a tenfold increase in photoluminescence (PL) intensity during photowashing, which provides unambiguous proof that PL enhancement does not require an activation step following photowashing. We also observe that the PL enhancement persists for at least 1 h under continued photowashing. Studies performed to elucidate the chemistry of PL enhancement indicate that sample history has a critical influence on experimental results, and that experimental details cannot be overlooked when comparing different experiments. We quantify the improvement in surface quality by measuring surface minority trapping velocities from luminescence decay profiles following picosecond optical excitation.