OBSERVATION OF WANNIER-STARK LADDER TRANSITIONS IN INXGA1-XAS-GAAS PIEZOELECTRIC SUPERLATTICES

Wannier-Stark ladder transitions in the photocurrent spectra of (111)B InxGa1-xAs-GaAs strained-layer piezoelectric superlattices are report ed. Both vertical transitions in the same well and diagonal transition s between adjacent wells are observed. In contrast to (100) superlatti ces, the Wannier-Stark spectra are observed for both senses of applied bias relative to zero potential drop across the superlattice. The obs erved transition energies are found to be in good agreement with the p redictions of exciton calculations. The piezoelectric field is deduced in a simple and direct way from analysis of the spectra as a function of bias.