Optical properties and Stokes shifts in lamp-annealed InGaAs/GaAs strained layer superlattice

The effect of incoherent lamp annealing on the photoluminescence and optical absorption characteristics in InxGa1−xAs/GaAs(x=0.2 and 0.24) strained layer superlattices grown by molecular-beam epitaxy has been investigated. The annealing time and temperatures were varied from 5–25 s and 850–950 °C, respectively. It is seen that the main photoluminescence and absorption peaks a low temperatures (11.5 K) shift to higher energies with increase in annealing temperatures. We believe this is due to In-Ga atomic interdiffusion across the heterointerfaces and have estimated the magnitude of this interdiffusion by solving the appropriate Schrodinger equation for this region. The estimated interdiffusion constants D are ∼10−16–10−15 cm2/s for the above annealing conditions, which are about three orders of magnitude higher than those reported for long-term furnace annealed InxGa1−xAs/GaAs(x=0.13–0.15). Optimal rapid thermal annealing has a significant effect in improving the quality of the superlattices in terms of Stokes shift and absorption coefficients. Extremely small Stokes shift ∼1.1 meV was observed for In0.2Ga0.8As/GaAs superlattices annealed at 890 °C for 5 s.