Wavelength Blue-Shifting and Gain Spectral Bandwidth of InAs/InP Quantum Dots for Laser Applications Around $1.55~\mu$ m

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.