EVIDENCES OF NON-COMMUTATIVITY AND NON-TRANSITIVITY OF BAND DISCONTINUITIES IN INP-AL(IN)AS-GA(IN)AS HETEROSTRUCTURES

In spite of the spatial separation of electrons and holes associated with its type II nature, the InP-Al(In)As system has so excellent optical properties that it is possible to measure the photo-luminescence excitation and the photo-current spectra in single heterojunctions. In addition, the bandgap of a type II heterostructure varies linearly with the discontinuity of the conduction bands. This system thus offers a unique opportunity for a detailed experimental study of the band offsets. We find that offsets at InP-Al(In)As and Al(In)As-InP heterojunctions are quite reproducible, but differ by (100 +/- 20 meV). Results in a series of superlattices are consistent with our observations in single heterojunctions, and show that the average band offset is not transitive in the Ga(In)As-InP-Al(In)As family of heterostructures.