Temperature dependent optical properties of single, hierarchically self-assembled GaAs/AlGaAs quantum dots

Abstract

We report on the experimental observation of bright photoluminescence emission at room temperature from single unstrained GaAs quantum dots (QDs). The linewidth of a single-QD ground-state emission (% 8.5 meV) is comparable to the ensemble inhomogeneous broadening (% 12.4 meV). At low temperature (T £ 40 K) photon correlation measurements under continuous wave excitation show nearly perfect single-photon emission from a single GaAs QD and reveal the single photon nature of the emitted light up to 77 K. The QD emission energies, homogeneous linewidths and the thermally activated behavior as a function of temperature are discussed.Keywords GaAs quantum dots AE Hierarchical selfassembly AE Single dot spectroscopy AE Room temperature luminescence AE Photon correlation PACS numbers 42.50.Ar AE 78.55.Cr AE 78.67.Hc During the last decade, much attention has been paid to the fabrication of semiconductor quantum dots (QDs) and to their optical properties. QDs have large oscillator strengths, narrow spectral linewidths, longterm stability, and can be easily integrated inside device structures (e.g., pillar microcavities) [1][2][3][4]. Single photon generation using single self-assembled QDs obtained by Stranski-Krastanow (SK) growth mode has been demonstrated at low temperature [5,6]. Single photons are useful for applications in quantum cryptography and quantum computation. Understanding the temperature dependence of QD emission is essential for making efficient devices, in particular at room temperature, where most devices operate.Recently, a novel growth technique was used to fabricate self-assembled GaAs/AlGaAs QDs [7]. These QDs offer several advantages compared to SK grown QDs: The grown material is ideally unstrained with sharp interfaces and emits light in the visible range. Because of the limited intermixing between QD and barrier material, the determination of the QD structural properties is affected by much less uncertainties compared to SK QDs. This renders the calculation of the QD optical and electronic properties easier [7][8][9][10] and makes these QDs an ideal playground to understand basic QD properties [11]. Moreover, the size and shape of the QDs can be substantially varied by tuning the growth parameters [7,8,12,13].The variation of the emission energy, the full width at half maximum (FWHM), and the quenching of the photoluminescence (PL) intensity of SK-grown QDs with increasing temperature have been extensively studied [see e.g., Refs. 14-16]. Peter et al. [17] have studied the asymmetric phonon sidebands on both the exciton (X) and biexciton (XX) emission lines in single GaAs monolayer fluctuation QDs. They showed that these sidebands are due to a nonperturbative coupling to the acoustic phonons. Because of the small lateral confinement in such QDs it is not possible to study their emission at temperatures higher than about 35 K. The origin of QD emission broadening and quenching at high temperature is still subject of debate.

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Narrow ridge waveguide high power single mode 1.3-μm InAs/InGaAs ten-layer quantum dot lasers

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