Threshold and Temperature Characteristics of InGa(N)As-GaAs Multiple Quantum Well Lasers
Licentiatavhandling, 2008

Semiconductor lasers emitting in the 1.3 μm regime are of interest for applications in access-networks like fiber-to-the-home and radio-over-fiber systems. Such fiber optical networks are expected to replace the copper-based access-networks currently in use due to a continuously increasing demand on user bandwidth. To facilitate a widespread implementation of such networks, low-cost semiconductor lasers emitting at 1.3 μm are needed. A significant improvement in cost efficiency is obtained with lasers capable of un-cooled operation. For this reason much research has been devoted to GaAs-based lasers which offer an inherent improved temperature stability compared to the temperature-sensitive InP-based lasers traditionally used. The work presented in this thesis deals with InGa(N)As multiple quantum-well (QW) lasers grown on GaAs, with the aim of improving and understanding their temperature characteristics. A performance comparison between InGaNAs/GaAs lasers and other GaAs and InP-based lasers is presented. The epitaxial material is grown by molecular beam epitaxy (MBE). By optimizing MBE growth conditions we have obtained record low values of threshold current density of 107 and 133 A/cm2/QW for triple QW 1.2 μm InGaAs and 1.3 μm InGaNAs lasers, respectively. A thorough investigation of the temperature dependence of the threshold current (Ith) for ridge wave guide InGaNAs double QW lasers is presented. The good temperature stability of such lasers is usually ttributed to large amounts of defect recombination as well as a large conduction band offset. This work, however, reveals that their good temperature stability also to a large extent arises from a significant and weakly temperature dependent lateral diffusion current, which is not an effect intrinsic to InGaNAs but rather related to the geometry of the laser cavity. By impeding lateral diffusion it should be possible to reduce Ith and still obtain a relatively good temperature performance.

GaAs

Semiconductor lasers

molecular beam epitaxy

multiple quantum wells

characteristic temperature

temperature dependence

dilute nitrides

ambipolar diffusion

InGa(N)As

Kollektorn, MC2
Opponent: Dr Bengt-Erik Olsson, Microwave and High Speed Electronics Research Center , Ericsson AB

Författare

Göran Adolfsson

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Ämneskategorier

Telekommunikation

Technical report MC2 - Department of Microtechnology and Nanoscience, Chalmers University of Technology: 128

Kollektorn, MC2

Opponent: Dr Bengt-Erik Olsson, Microwave and High Speed Electronics Research Center , Ericsson AB