Excitation energy dependence of the optical properties of InGaAs/GaAs quantum well heterostructures

Abstract

We report an experimental study on a large set of InGaAs/GaAs quantum well structures by means of continuous-wave photoluminescence and photoluminescence excitation. The luminescence spectrum at low temperature systematically exhibits a doublet structure whose lineshape is very sensitive to the excitation energy. Accordingly, the excitation spectra detected by monitoring the emission at the two different luminescence peaks have very different profiles, with peaks and/or dips which are not directly related to absorption resonances. As a matter of fact, the anomalies disappear when increasing the temperature or when using an optical bias with energy above the GaAs energy gap. In these cases, the excitation profiles recover the behaviour typical of 2D systems. PACS 78.66.Fd -III-V semiconductors. PACS 73.20.Dx -Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds). PACS 71.35 -Excitons and related phenomena (including electron-hole drops). PACS 78.55.Cr -III-V compounds and systems. PACS 01.30.Cc -Conference proceedings.InGaAs/GaAs strained-layer quantum wells (QW) exhibit a wider variety of relevant physical properties, when compared to GaAIAs/GaAs lattice-matched heterostructures, which makes them very interesting for device-related applications. This is due to the presence of strain[l], interface segregation[2], and large heavy-light-hole splittings. A correct characterization of the optical properties of these structures is therefore required and extremely useful.