InP/GaInP Quantum Dot Lasers

Abstract

Over the last decade self-assembled semiconductor quantum dots have become a major issue in semiconductor physics [1–3] — both from a fundamental point of view as well as in respect to applications such as the quantum dot laser. Originally, the quantum dot laser was proposed to outperform the well-established quantum well laser on the basis of properties such as material gain [4], differential gain [4], temperature stability [5] and threshold current density [4, which directly results from the zero-dimensional density of states of quantum dots. By now several predicted superior properties have indeed been successfully demonstrated [6, 7]. However, the main breakthroughs were not caused by any physical virtues, but occurred on the basis of technological inventions. Huffaker et al., for example, demonstrated 1.3 µm emission of a quantum dot laser grown on a GaAs (001) substrate [8]. This emission wavelength is impossible to reach with conventional InGaAs/GaAs quantum wells on a GaAs substrate. As a consequence InAs/GaAs quantum dots are highly attractive for the use in both edge emitting devices (see also Sect. 13.4) as well as vertical cavity surface emitting lasers (VCSELs) [9] (see also Sect. 13.6).