In-plane ultrahigh-density InAs quantum dots (QDs) were grown on the GaAsSb buffer layer by molecular beam epitaxy. Photoluminescence (PL) properties of the InAs QDs/GaAsSb layer were measured under 1.58 eV and 1.44 eV light excitations, which were GaAs and InAs QD/wetting layer (WL)/GaAsSb excitations. For the GaAs excitation, PL spectra were due to a type-II transition from the ground state (GS) of the QD conduction band to the GaAsSb valence band. This PL spectrum did not depend on the measurement position because of the electron filling into lower GS levels. For the InAs QD/WL excitation, PL spectra originated from the crossed transitions of localized bound excitons between QD excited states (ES) and the WL valence band, and depended on the measurement position. Furthermore, excitation power and temperature dependences of the PL spectra were measured to discuss carrier dynamics.

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Self-assembled InAs/InAsSb ultrahigh-density quantum dots (UHD QDs) were grown on GaAs(001) substrate by molecular beam epitaxy. The QD density was 1×1012 cm-2, and an average separation distance between adjacent QD edges was less than 3 nm. The temperature dependence of photoluminescence (PL) minimum energy of UHD QDs was measured and was divided clearly into three temperature regions: (1) fitting to upper Varshni shift at 15 K to 80 K, (2) decreasing from upper Varshni shift from 80 K to 180 K and (3) re-fitting to lower Varshni shift at 180 K to 290 K. The energy difference between upper and lower Varshni curves increased with increasing QD density. This anomalous temperature dependence of PL minimum energy was demonstrated by a simulation model of miniband formation due to electronically strong coupling of adjacent QDs, including the temperature dependence of the homogeneous broadening in the QD.