Capture of photoexcited carriers in a single quantum well with different confinement structures

The authors report experimental and theoretical studies of photoexcited carrier trapping in a GaAs/Al_xGa_1-xAs single quantum well with three different typical confinement layer structures: a separate-confinement heterostructure (SCH) and a graded SCH (GRIN-SCH), a linearly graded SCH (LGRIN-SCH), and a parabolically-graded SCH (PGRIN-SCH). The capture is studied by means of time-resolved luminescence with 600-fs resolution. Measurements, performed from 20 to 300 K, show an appreciably shorter trapping time in the GRIN-SCH (1 ps at 80 K to 8 ps at 300 K) than in the SCH (between 22 and 14 s in the same temperature range). Experimental results are fitted by a one-dimensional drift-diffusion model, and the mobility of holes is deduced from the calculations. A short but finite capture time at the edge of the well is demonstrated