Optical characterisation of InAs/GaAs structures grown by MBE

In the present work we have investigated the optical properties of the strained InAs/GaAs submonolayers. The InAs thickness varies from 0.5 to 2 atomic monolayers (ML). Samples are grown by molecular beam epitaxy (MBE) on (001) 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. Thinner 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 amount, is accompanied by a shoulder at 1.32 eV. These two lines appear when the excitation energy is near the carbon absorption (e-A°) in GaAs. Their exact natures are not yet known and are associated to the radiative recombination on Cu impurity in semi-insulating GaAs substrate and its satellite phonon replica.