PHOTOLUMINESCENCE AND PHOTOTHERMAL DEFLECTION SPECTROSCOPY OF INAS QUANTUM-DOT SUPERLATTICES GROWN ON GAAS BY MOLECULAR-BEAM EPITAXY

In this report, we apply simultaneously the measurements of luminescen ce and absorption to InAs/GaAs quantum dot superlattices grown on GaAs substrates. It is found that the peak energy obtained by a radiative process increases with decreasing dot size due to the effect of quantu m confinement. Because the size of the quantum dots that we studied is significantly larger than that of dots in previous reports, we are ab le to justify the theoretical calculation of the transition energy in InAs dots grown by molecular beam epitaxy. A highly sensitive techniqu e of photothermal deflection spectroscopy (PDS) is used as the absorpt ion technique. We show that PDS is more than sufficient to measure opt ical absorption in thicknesses of a few atomic layers. The obtained ba nd-gap energies for different sizes of InAs quantum dots can be predic ted accurately by the quantum confinement effect and agree well with t he results of photoluminescence measurements. We demonstrated that PDS is an alternative tool for the study of nano-structure devices.