Optical characterisation of InAs/GaAs structures grown by MBE

In the present work we have investigated the optical properties of the stra ined InAs/GaAs submonolayers. The InAs thickness varies from 0.5 to 2 atomi c monolayers (ML). Samples are grown by molecular beam epitaxy (MBE) on (00 1) GaAs substrates and characterised by photoluminescence spectroscopy (PL) . The PL spectrum of 2ML's sample exhibits only one broad line which comes from 3D structures and shows the presence of self-organised quantum dots. T hinner sample shows responses of two PL bands. The first one, which shows a red shift for increasing the In amount, is associated to the luminescence from 2D structure. The second one at 1.36 eV, not sensitive to the InAs amo unt, is accompanied by a shoulder at 1.32 eV. These two lines appear when t he excitation energy is near the carbon absorption (e-A degrees) in GaAs. T heir exact natures are not yet known and are associated to the radiative re combination on Cu impurity in semi-insulating GaAs substrate and its satell ite phonon replica. (C) 2000 Elsevier Science S.A. All rights reserved.