Metamorphic InAs/InGaAs quantum dot structure: photoelectric study

The photoluminescent and photoelectric properties of a metamorphic InAs/In0.15Ga0.85As structure with InAs quantum dots (QDs) grown on an InGaAs metamorphic buffer (MB) layer are studied. The structure shows the an efficient photoluminescence (PL) signal at 0.93 eV and a week weak band by the InAs wetting layer near 1.2 eV at room temperature (RT), the bands shift to 1.02 and 1.26 eV respectively being cooled to 10 K. Spectral position of the QD emission band corresponds to the telecom window at 1.3 µm (0.95 eV). The structure with vertical contacts is found to be photosensitive in the spectral range above 0.9 eV at RT. All the components of the structure from QDs at 0.9 eV to the MB above 1.22 eV are observed in the photovoltage and photoconductivity spectra. The indirect effect of GaAs manifests itself as only with the drop of the signal at 1.36 eV. No effect of defect centers on the PL and photoelectrical properties is found, although they are observed in the absorption spectrum. The band structure provides a good collection of charge carriers to the InAs QDs which leads to high PL signal. These results confirm that the proposed metamorphic QD structure is a viable option for the development of optoelectronic devices, as the presence of defects due to strain relaxation of the MB does not forbid an efficient collection of carriers into QDs.