Magnetophotoluminescence study of the influence of substrate orientation and growth interruption on the electronic properties of InAs∕GaAs quantum dots

Abstract

We have used photoluminescence in pulsed ͑ഛ50 T͒ and dc ͑ഛ12 T͒ magnetic fields to investigate the influence of substrate orientation and growth interruption (GI) on the electronic properties of InAs/ GaAs quantum dots, grown by molecular beam epitaxy at 480°C. Dot formation is very efficient on the ͑100͒ substrate: electronic confinement is already strong without GI and no significant change in confinement is observed with GI. On the contrary, for the ͑311͒B substrate strong confinement of the charges only occurs after a GI is introduced. When longer GIs are applied the dots become higher.

Magneto-optical study of thermally annealed InAs-InGaAs-GaAs self-assembled quantum dots

“…The Faraday geometry reduced mass would represent the combination of the electron mass and a small hole mass, with the Voigt mass being close to that of the electron. The present masses determined for the Faraday geometry are reasonably consistent, although slightly lower, than values (0.11~0.13m 0 ) previously reported for InAs QDs and determined using the same magneto-PL technique [17,19]. However, if the Voigt geometry mass does reflect that of the electron it appears rather large, for example Pryor [24] calculates a spatially averaged electron mass in InAs QDs of ~0.042m 0 although it is unclear if this includes enhancements due to nonparabolicity.…”

“…However, for the Voigt geometry the relatively small height of the dots generally prevents the high field limit 2 2 > e B ρ h being attained over a sufficiently large field range, hence preventing a determination of the reduced mass and the extent of the exciton along the growth axis [17,19,20]. In the present studies the high field limit is reached for both geometries at relatively low fields, allowing a comparison of inplane and growth direction parameters.…”

“…Magneto-PL spectra were recorded at 4.2 K in fields up to 50 T in a pulsed magnet system. 532 nm exciting light was transmitted to the sample via a 200 μm-core optical fibre, with a bundle of six similar fibres used to collect the resultant PL [17]. The PL was detected by a cooled InGaAs diode array.…”

Self-assembled InAs quantum dot formation on GaAs ring-like nanostructure templates

“…4b shows the curve at a lasing power density of 1.26 W/cm 2 , both at 10 K. The peak of this sample's curve at 1.26 W/cm 2 excitation in Fig. 4b is centered at 1.264 eV, and the full-width halfmaximum (FWHM) is 22.3 meV, less than the FWHM of the PL of typical InAs QDs [26]. Also, there is negligible shift in energy in the ground state curve peak when the excitation was increased to 40 W/cm 2 , giving an indication that QDs retain the same energy states for the ground state excitonic recombinations.…”

GaSb quantum dot morphology for different growth temperatures and the dissolution effect of the GaAs capping layer

“…Although the issue of capping and its influence on the QDs' properties has been studied extensively, this has been largely restricted to the InAs/GaAs system [18][19][20]. There are only a few papers on the growth of GaSb QDs [14][15][16][17][21][22][23][24][25]32], and the specific issue of capping has not been addressed, even though effects may be more pronounced than in InAs/GaAs. Indeed, our data show that Sb-As exchange during capping is prevalent, and that it leads to dissolution of the dots unless a low capping temperature is used.…”