SOME INVESTIGATIONS OF THE PHYSICAL-PROPERTIES OF (GA,IN)AS-GAAS HETEROSTRUCTURES GROWN WITH BUILT-IN PIEZOELECTRIC FIELD

The properties of single and double (Ga,In)As-GaAs strained-layer quan tum wells embedded in (pin) diodes are studied. These properties are f ound to be orientation-dependent, mainly due to the existence of a str ong internal piezoelectric field in the (Ga,In)As layers when the grow th axis is polar. We first calculate how large the influences of the ( pin) and piezoelectric field are to produce carrier tunnelling out of the active part of the heterostructure. This enables us to compute the carrier's lifetime in the heterostructures and the corresponding reso nance widths. Next, we compare the binding energies of interacting ele ctron and hole pairs in double quantum wells with or without internal piezo electric fields. We show that the exciton binding energy is less sensitive to the piezoelectric field than the oscillator strength. Un der photo excitation, many body-effects and bandgap renormalization ca n be easily produced in strained-layer quantum wells with internal bui lt-in piezo-electric fields. We illuminated at low temperature single and double Ga0.92In0.08As-GaAs strained layer quantum wells grown eith er along the (001) or (111) direction, and tuned over several decades the densities of photo-injected carriers. The comparison between exper imental data and the results of a Hartree calculation including the sp ace charge effects reveals that many body interactions are efficiently photo-induced in the (111)-grown samples. Moreover, we show that the tunnelling of the two lowest-lying heavy-hole levels can be stimulated for moderate carrier densities making such structures promissive in o rder to realise self electrooptic effect device (SEED) modulators.