Abstract

A spatial resolution of <1 µm is demonstrated for photoluminescence (PL) measurements from a 3-nm quantum well GaAs/AlGaAs graded-index separate confinement heterostructure by using a confocal PL arrangement that includes an aperture in the illumination optics path that is imaged onto the sample and a conjugate aperture in the collection optics path. By translating this second aperture, a direct measurement of the carrier diffusion length (~5 µm) is obtained. This technique provides a spatial resolution limited only by the optics rather than by the carrier diffusion, as is the case in most semiconductor PL measurements. The capabilities of this technique are further illustrated in monitoring the spatial dependence of the carrier transport for a transversely graded thickness quantum well formed by MOCVD growth over a cleaved sample edge. Effects observed include variations of the PL wavelength and efficiency with dramatic effects near the sample edge and an asymmetry in the diffusion parameters near this edge, providing evidence for enhanced carrier transport towards the wider portion of the well.

© 1992 Optical Society of America