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It was found experimentally that growing an ultrathin GaP interlayer/sublayer before InAs quantum dots (QDs) grown on InGaAsP barrier lattice-matched to InP (001) substrates is an efficient way to tune the emission wavelength of InAs/InP QD lasers to 1.55 μm range at room temperature (RT). However, the impact of interlayers/sublayers in InAs/InP QD lasers has not been carefully investigated and analyzed theoretically, and the existing physic model cannot predict the emission wavelength of InAs/InP QD lasers engineered by interlayers/sublayers. In this paper, an improved model, which consists of a three-step strain analysis, is applied to precisely predict measured photoluminescence emissions of various QD samples with the GaP interlayer/sublayer that have a specific thickness or chirped/varied thicknesses at both RT and low temperature. It is found that the impact of the GaP sublayers is to enhance quantum confinement instead to stop As/P exchange. Finally, a new method of emission spectrum blue-shifting and gain spectral bandwidth enhancement of an InAs/InP QD laser is proposed and found to be more efficient. By optimizing sublayer thickness and double capping, a total gain spectral bandwidth of 245.7 nm, as an example, is predicted and peak wavelength is shortened to 1500 nm. [ABSTRACT FROM AUTHOR]

The double-capping procedure has been widely used to control the size distribution of self-assembled InAs/InGaAsP quantum dots during the growth on a (001) InP substrate. However, the conventional simulation method referred to one-step model does not include this procedure, which may lead to inaccuracy in modeling of quantum dots. An accurate method of modeling a single quantum dot including a thorough elastic strain analysis is proposed and developed in this paper. The confinement potential profiles are found significantly different between the two models. A series of settings (i.e., dot heights, dot base sizes, and dot shapes) is considered. The electronic band structure is calculated by using the eight-band $k \cdot p$ model. By comparing with the photoluminescence measurements in previously published works, it is found that the obtained optical transition energies using the accurate two-step model are in better agreement. The bright exciton splitting is found larger in terms of fine structures. Moreover, the impact of the quaternary compositions (arsenic mole fraction) of barrier material is for the first time systematically studied by using this accurate model. [ABSTRACT FROM AUTHOR]