Growth and properties of self assembled indium arsenide quantum dash laser active regions.

摘要

Self-organized growth mechanisms have been intensively investigated for the last decade as a powerful way to achieve a variety of high quality quantum confined structures. Among these varieties is the growth of InAs quantum dashes on InP. This dissertation discusses the growth aspects of quantum dashes and their application as active regions in semiconductor laser diodes. A comprehensive study on MBE growth conditions and structural and optical properties of quantum dashes is conducted as well as an investigation of the influence of the quantum dashes on performance parameters of the laser diodes.;The main parameters that influence the structural asymmetry of the quantum dashes have been identified as the InAs coverage as well as surface morphology and the strain with respect to the base crystal, on which the quantum dashes are grown. The optical emission wavelength is defined by the size of the quantum dashes and the quantum well, in which the dashes are incorporated, and ranges from less than 1.47 mum to beyond 2 mum.;Diode lasers based on the quantum dashes as active medium with 2 mum emission wavelength have been fabricated and characterized. On the short wavelength side, lasers with emission at 1.47 mum have been grown. These are the longest and shortest wavelengths achieved with quantum dash lasers on InP.;A comparison of the beam quality of quantum dash lasers with that of equivalent quantum well lasers reveals no advantage of quantum dashes over quantum wells. This is consistent with other investigations on the linewidth enhancement factor associated with quantum dashes and quantum wells.;A study on the link between the morphological anisotropy and the optical polarization anisotropy of quantum dashes shows that the polarization anisotropy reduces upon coverage of the dashes, and that the correlation between optical anisotropy of covered dashes with the morphological anisotropy of exposed dashes is very low. Growing structurally more symmetric dot-like quantum dashes does not turn their optical properties into those of quantum dots.