Optical study of inverted interface in InP/InAlAs/InP structures grown by MOCVD

By comparing the PL spectra taken for two double heterostructures InP-InAlAs-InP grown by MOCVD on (311)(B) and (100) substrates we have shown that the heterostructures grown on (311)(B) have better optical quality than the one grown on (100). The main reason for this is the fluctuation of composition within the second sample. Thus, we have focused our studies in this work, by photoluminescence (PL) and linear polarized photoluminescence spectroscopy (PPL), on the staggered band lineup inverse interface of the InP/InAlAs/InP double heterostrcture grown on (311)(B). At low temperature, this interface induces a photoluminescence transition at 1.25 eV, thus giving a new possibility to achieve an optical emission with a photon energy smaller than the band gap energy of both semiconductors forming the heterostructure. It can be shown that this luminescence line shifts logarithmically towards higher energy when the injection is increased. PPL experiments reveal a variation of a degree of polarization for normal and inverted interface transition. This suggests that the two interfaces are not equivalent. On the other hand, for heterostructure grown on (100) substrate and for high laser injection we observe a new luminescence band on the high energy side of the luminescence in InAlAs bulk material. This new emission is attributed to a luminescence of a disordered superlattice due to composition modulation related to the value of the V/III molar ratio. (C) 2000 Elsevier Science B.V. All rights reserved.