Comparison of material properties and laser device characteristics of indium phosphide-based quantum confined structures.

摘要

Self-assembled semiconductor quantum dots (QDs) constitute a class of nanoscale materials which provide fundamental advantages compared to the dominating 2D quantum-well (QW) structures in photonic device applications. Since the first demonstration in early 80s, the fundamental optical and electrical properties of InGaAs/GaAs QD structures have been relatively well studied. The realization of QD lasers well beyond 1.3 mum on GaAs substrate remains a great challenge. Recent attempts to extend the technology of self-assembled growth of QDs on InP substrate has led to the development of InAs-based quantum-dot/dash (QD/Dash) that gives the ground state transition spans over several bands of optical telecommunication windows between 1.4-1.7 mum wavelengths. Due to quasi-three-dimensional carrier confinement and intrinsic properties, Qdash enables several interesting laser diode characteristics such as potentially improved temperature insensitivity, optical feedback resistance, and wideband amplification.;Although high performance devices such as lasers and optical amplifier have been fabricated using these material systems, fundamental optical and electrical properties of the InAs/InP Qdash and Qdash-in-well structures have not been systematically studied. In this dissertation, one of our objectives is to perform different intermixing technologies on GaAs- and InP-based quantum nanostructures. Various spectroscopy techniques have been applied to study the effect of InAs/InP quantum dash-in-well active gain medium of semiconductor lasers on the optical beam quality and coupling efficiency. Various electrical and optical techniques are performed at the device level to gain physical insights of the Qdash structures. The far field profiles of QD, QDash and QW lasers have also been studied. We found that the nature of carrier diffusion of Qdash and QW lead to the different degrees of filamentation and QD has better optical beam quality due to the three dimensional confinement of carriers.;The orientation dependent emission of quantum dash-in-well structure, TE and TM polarization degree, have also been investigated. In our study, we found that polarization insensitive gain of InAs/InGaAs Qdash structure can be achieved utilizing the proper stacking number of Qdash layer and the angle of the Qdash alignment.