Resolving exciton diffusion in InGaAs quantum wells using micro-photoluminescence mapping with a lateral excitation.

We report a spatially resolved photoluminescence mapping of InGaAs quantum wells. The photoluminescence was collected on top of the quantum well, with a HeNe laser pumping horizontally or vertically. In the horizontal configuration, at temperature of 68 K, the spectral linewidth narrows from 2.8 to 2.2 meV with the peak shifting from 1.4425 to 1.4415 eV, while at 3.8 K these changes were not observed. This demonstrates that photo-generated carriers can diffuse away from the laser spot and relax to the lower energy states in the case when the charge carriers are thermally activated. The spectra narrowing in the vertical configuration, which could not be observed, is due to the fact that the emitted light was always collected from the same spot of the pumping laser without diffusion. [ABSTRACT FROM AUTHOR]