Abstract
An optical study of a series of high quality piezo-electric (PZ) (111)B GaAs-(InGa)As strained multi-quantum wells is reported. Well defined Δn≠0 transitions (E1HH2, E1HH3 and E2HH1) are observed with comparable strength to the Δn=0 transition, as a result of the asymmetric well profile induced by the piezo-electric field. In PLE the onset of the E1HH1 continuum is clearly seen, allowing the deduction of an exciton binding energy of 9 meV. Appyting a bias to oppose the PZ field reduces the field in the well, which decreases the quantum confined Stark shift and weakens the Δn≠0 transitions. At high bias, corresponding to flat band in the well, strong lifetime broadening is observed. Good agreement between theory and experiment is found only by using a value for the PZ constant ∼30% smaller than the commonly accepted value.
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