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The optical properties of shape-engineered InAs/InAlGaAs quantum dots (SEQDs) were investigated by temperature-dependent and excitation-power-dependent photoluminescence (PL) spectroscopy and compared with those of the conventionally grown InAs QDs (CQDs). The emission wavelength of the InAs/InAlGaAs SEQDs at 240 K was redshifted by 18 nm from that at 15 K, which was relatively smaller than that of the InAs CQDs (97 nm). The PL yield at 240 K was reduced to 1/86 and 1/65 of that measured at 15 K for the InAs CQDs and the InAs/InAlGaAs SEQDs, respectively. The emission wavelength for the InAs CQDs was blueshifted by 76 nm with increasing excitation power from 0.56 to 188 mW, compared to only by 7 nm for the InAs/InAlGaAs SEQDs. These results indicated that the InAs/InAlGaAs SEQDs were optically more stable than the InAs CQDs mainly due to the enhancement of the carrier confinement in the vertical direction and the improvement in the size uniformity.
Yang et al. (Sun,) studied this question.