MBE growth optimization and optical spectroscopy of InAs/GaAs quantum dots emitting at 1.3 μm in single and stacked layers

V Celibert,E Tranvouez,G Guillot,C Bru-Chevallier,L Grenouillet,P Duvaut,P Gilet,P Ballet,A Million

doi:10.1016/j.jcrysgro.2004.11.370

Abstract

Self-organized InAs quantum dots (QDs) are grown in the Stranski–Krastanov regime, by molecular beam epitaxy, on (1 0 0) GaAs substrates. In order to grow high-quality QDs emitting at 1.3 μm, an unusual two-step growth procedure is first developed, with a growth interruption during the InAs deposition, just above the critical thickness. Then two important growth parameters are considered. First, the GaAs cap layer deposition rate is optimized, the InAs growth being kept constant. Second, the InAs growth rate is optimized, at optimized GaAs cap layer deposition rate. The optimizations leads to large QDs with a unimodal size distribution and the room temperature photoluminescence (PL) spectrum peaks at 1.3 μm with a 19 meV full-width at half-maximum (FWHM). These optical properties are at the international state of art. Then, three QD layers are stacked with different spacer thickness in order to increase the QD density necessary for laser applications. The best optical properties are obtained for the wider GaAs spacer (45 nm): PL emission around 1.3 μm, narrow FWHM (31 meV), and PL intensity enhanced by a factor of 3. The results are promising for further incorporation of the QD stacks in the active region of a laser.

Highlights

Low-dimensional carrier confinement nanostructures such as quantum wires and dots are quite attractive for applications to high-performance electronic and optical devices such as lasers [1,2]
Another advantage of such a two-step procedure is an increase in PL intensity as observed in Fig. 1 because a maximum of quantum dot (QD) emit around the same energy
A two-step growth procedure is proposed for the growth of high-quality InAs QDs on GaAs substrates

Summary

Introduction

Low-dimensional carrier confinement nanostructures such as quantum wires and dots are quite attractive for applications to high-performance electronic and optical devices such as lasers [1,2]. The realization of optically active QDs emitting in the desired spectral range has no meaning for laser applications if the structures do not provide the benefits of low threshold current and hightemperature stability To access these features, the full-width at half-maximum (FWHM) of the quantum dot (QD) photoluminescence (PL) needs to be as small as possible (state of the art is less than 20 meV [5,6]) and a high-density of self-assembled QDs is required to enhance the optical gain. The full-width at half-maximum (FWHM) of the quantum dot (QD) photoluminescence (PL) needs to be as small as possible (state of the art is less than 20 meV [5,6]) and a high-density of self-assembled QDs is required to enhance the optical gain The influence of both GaAs cap layer and InAs deposition rates on the growth of self-assembled InAs/GaAs QDs has already been studied separately in Refs. The influence of GaAs spacer thickness on the optical properties is studied

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