EXCITON BINDING-ENERGIES AND PHOTOINDUCED TUNNELING OF CARRIERS IN (GA,IN)AS-GAAS HETEROSTRUCTURES GROWN WITH BUILT-IN PIEZOELECTRIC FIELD

We compare the binding energy of interacting electron and hole pairs i n double quantum wells with and without internal piezo-electric fields . We show that the exciton binding is less sensitive to the piezo elec tric field than the oscillator strength. This allows many body-effects and bandgap renormalization to be easily produced in strained-layer q uantum wells with internal built-in piezo-electric fields, under photo excitation. Our observation was made at low temperature by comparing the behaviour of Ga0.92In0.08As-GaAs strained layer single and double quantum wells grown along the (001) and (111) directions when the dens ities of photo-injected carriers are tuned over several decades. Compa rison between experimental data and the results of a Hartree calculati on including the space charge effects reveals that manybody interactio ns are efficiently photo-induced in the (Ill)-grown samples. Moreover, tunnelling of the two first excited heavy-hole levels can be stimulat ed for moderate carrier densities making such structure promissive for realising self electrooptic effect device (SEED) modulators.