Optical studies of InP/InAlAs/InP interface recombinations

We report on the photoluminescence characterization of a metalorganic vapour phase epitaxy grown InP/InAlAs/InP structure. The energy band alignment of the InAlAs/InP interface is of type II. The PL arising from the first grown interface (InAlAs grown on InP) is clearly seen at 1.2 eV. The localization was possible by scanning the laser beam on a angle-bevelled sample whose bevel crosses all the layers of the InP/InAlAs/InP structure. For the second interface, called the inverse interface (InP grown on InAlAs), a different PL behaviour is observed. The energy of the observed PL peak is 1.3 eV. It is very sensitive to the excitation power. From this behaviour, the Auger depth profiling measurements and the wedge transmission electron microscopy performed on this sample we conclude that this recombination does not originate from a type II interface band structure but from an InAsxP1-x layer located at the inverse interface. This intermediate layer originates from the higher incorporation coefficient of As compared to that of P.