SANDiE Partner P12

Institut National des Sciences Appliquées de Rennes (INSA-LENS), France

During the last period, efforts have been devoted to improve the growth of InAs/InP QD structure in order to develop 1.55 µm low chirp lasers and large wave band amplifiers. This work has been supported by optical characterizations and modelling with other SANDIE partners.

(M) InAs/InP(113)B QD Growth has been optimised in order to reach high density low size dispersion of QDs emitting around 1.55 µm. In particular, the As2 flux has been determined to play a major role on the QD growth on InP(113)B substrate. A reduction of As2 flux during QD growth leads to a drastic increase of the density up to 1.1×1011 dots/cm2, along with a reduction of the size dispersion. Investigations have also been performed to study the role of the quaternary buffer composition layer on the QD growth. The effect of QD stacking on the structural properties has been studied by AFM. The role of the interdot spacer layer has been assessed. For the optimized conditions QD stacking present a very good vertical and lateral ordering and a low size dispersion. The PL linewidth of six QD stacked layers reduced to 40 meV.

(O) We have also conducted various optical characterizations in order to study the impact of growth parameters on the QDs electronic properties. Magneto-photoluminescence experiments have been performed with partner 2 to obtain fundamental parameters such as the effective mass, the exciton radius and binding energy for different growth procedure samples (PhD student C. Cornet).

Optical absorption have been measured and confronted to simulations. High intensity PL measurements have revealed the energy splitting between QDs fundamental and excited state transitions. Polarization anisotropy is under study for the amplifier operation.

(C) Collaboration with TUB (P4) has been intiated on k.p multiband approach, taking into account the strain and piezoelectric effects, for the calculation of InAs/InP electronic properties. A PhD student (C. Cornet) has been trained to use the TUB software. Development is under way.

(D) Optimized laser structure Laser present improved performances. In particular a record low threshold current density of 190 A/cm2 is achieved for a cavity length of 3 mm. The extrapolated threshold current density for infinite cavity length is estimated at 7 A/cm2 by QD layer which is closed the theoretical value. Laser state of the art InAs/InP (311B) structures have been provided to LPN-Marcoussis (P11) by a PhD student (E. Homeyer) for Single mode laser processing and testing. Pump probe experiments on InAs/InP 311B QDs are being carried out for saturable absorption.

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last update: 28 February 2019, A. Weber