Observation of spinodal phase separation and quantum dot formation in InGaAs/GaAs layers grown at down-ramped growth temperatures

We observed spinodal phase separation in In_xGa_1-x As layers grown on GaAs substrates at decreasing growth temperatures. The phase separation results in quantum-wire like structures for high In content (x=0.2) and low rates of temperature decrease (0.1°C/s). With faster rates of temperature decrease (0.3°C/s) and a decreased In content (x≈0.03) formation of island-like structures is observed. The islands show photoluminescence emission of high intensity and comparatively narrow linewidth (≈30 meV). Calorimetric absorption spectroscopy (CAS) was carried out at T=500 mK, where particularly high sensitivity is realised, in order to confirm confinement of carriers in these structures