Competition between tunneling and exciton formation for photoexcited carriers in asymmetric double quantum wells.

The formation of excitons from photoexcited free carriers in a GaAs asymmetric double quantum well tunneling structure is shown to occur by a bimolecular process. Using the non-linear luminescence cross- correlation technique, a bi-molecular formation coefficient of 6x10highminus12qcm/ps is determined. The electron and hole tunneling times are also simultaneously obtained.