Growth and characterization of InAs columnar quantum dots on GaAs substrate

The growth of InAs columnar quantum dots (CQDs) on GaAs substrates by MBE was studied. The CQDs were formed by depositing a 1.8 monolayer (ML) InAs seed dot layer and a short period GaAs/InAs superlattice (SL). The growth of the CQDs is very sensitive to growth interruption (GI) and growth temp. Both longer GI and higher growth temp. impact the size dispersion of the CQDs, which causes the broadening of photoluminescence (PL) spectrum and the presence of the addnl. PL peak tails. By properly choosing the GI and the growth temp., CQDs including GaAs (3 ML)/InAs (0.62 ML) SL with period no. up to 35 without plastic relaxation were grown. The corresponding equiv. thickness of the SL is 41 nm which is two times higher than the theor. crit. thickness of the strained InGaAs layer with the same av. In compn. of 16%. The increase of the crit. thickness is partially assocd. with the formation of the CQDs. Based on a five-stack CQD active region, laser diodes emitting around 1120 nm at room temp. were demonstrated, indicating a high material quality. CQDs with nearly isotropic cross section (20 nm*20 nm dimensions) were formed by depositing a 16-period GaAs (3 ML)/InAs (0.62 ML) SL on an InAs seed dot layer, indicating the feasibility of artificial shape engineering of QDs. Such a structure is expected to be very promising for polarization insensitive device applications, such as semiconductor optical amplifiers. [on SciFinder (R)]