SOME INVESTIGATIONS OF THE PHYSICAL PROPERTIES OF (Ga, In)As-GaAs HETEROSTRUCTURES GROWN WITH BUILT-IN PIEZOELECTRIC FIELD

Abstract

The properties of single and double (Ga,ln)As-GaAs strained-layer quantum wells embedded in (pin) diodes are studied. These properties are found to be orientation-dependent, mainly due to the existence of a strong internal piezoelectric field in the (Ga,ln)As layers when the growth 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 resonance widths. Next, we compare the binding energies of interacting electron 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. Under photo excitation, many body-effects and bandgap renormalization can be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields. We illuminated at low temperature single and double Ga 0.92 ln 0.08 As-GaAs strained layer quantum wells grown either along the (001) or (111) direction, and tuned over several decades the densities of photo-injected carriers. The comparison between experimental data and the results of a Hartree calculation including the space 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 order to realise self electrooptic effect device (SEED) modulators.