Exciton binding energies and photo-induced tunnelling of carriers in (Ga,In)As-GaAs heterostructures grown with built-in piezoelectric field

Abstract

We compare the binding energy of interacting electron and hole pairs in double quantum wells with and without internal piezo-electric fields. We show that the exciton binding is less sensitive to the piezo electric field than the oscillator strength. This allows many body-effects and bandgap renormalization to be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields, under photo excitation. Our observation was made at low temperature by comparing the behaviour of Ga 0.92 In 0.08 gAs-GaAs strained layer single and double quantum wells grown along the (001) and (111) directions when the densities of photoinjected carriers are tuned over several decades. Comparison between experimental data and the results of a Hartree calculation including the space charge effects reveals that manybody interactions are efficiently photo-induced in the (111)-grown samples. Moreover, tunnelling of the two first excited heavy-hole levels can be stimulated for moderate carrier densities making such structure promissive for realising self electrooptic effect device (SEED) modulators