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

Abstract

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.