Temperature dependent and time-resolved photoluminescence studies of InAs self-assembled quantum dots with InGaAs strain reducing layer structure

Abstract

Four types of self-assembled InAs/GaAs quantum dots (QDs) were grown by molecular beam epitaxy and studied via temperature-dependent and time-resolved photoluminescence (PL) spectroscopy measurements. A thin InGaAs stain reducing layer (SRL) is adopted which extends the emission wavelength to 1.3 μm and the influence of strain on QDs is investigated. The SRL releases the strain between the wetting layer and QDs, and enlarges the size of QDs, as shown by atomic force microscopy measurements. As the thickness of InAs layer decreases to 1.7 ML, the QDs with the SRL are chained to strings and the density of QDs increases significantly, which leads to an abnormal redshift of 1.3 μm PL peak at room temperature. PL peaks of InAs QDs with the SRL show redshift compared with the QDs directly deposited on GaAs matrix. The dependences of PL lifetime on the QD size, density and temperature (T) are systematically studied. It is observed that the PL lifetime of QDs is insensitive to T below 50 K. Beyond 50 K, increases and then drops at higher temperature, with a peak at TC, which was determined by the SRL and the thickness of InAs. We have also observed an obvious PL spectral redshift of the QDs with 1.7 ML InAs coverage on SRL at low T as the measuring time delays. The PL lifetime of QDs with the SRL is smaller than that of QDs without the SRL. The QDs with different densities have different PL lifetime dependence on the QDs size. These observations can be explained by the competition between the carrier redistribution and thermal emission.

Coulomb effect inhibiting spontaneous emission in charged quantum dot

“…The emission energy shift and intensity modification processes are mutually coupled; when the transition exhibits a normal decay phase, no further changes to the peak position occur, as observed under the low-power measurements. 9 Time-resolved experiments performed on similar tunnel injection structures under low-excitation density ͑three to four orders of magnitude lower than used in our experiment͒ showed only an increase in the emission intensity before the exponential decay 10,11 and were interpreted as a slow transfer time between the well and the dots. In our case we observe that the initial rise time of all states is comparable to the temporal resolution of the experiment, which clearly indicates that the transfer between the QW and the QDs is of the order of tens of picoseconds, consistent with Ref.…”

Influence of InAs Coverage on Transition of Size Distribution and Optical Properties of InAs Quantum Dots

“…4a and b, respectively. With increasing temperature, all spectra show a typical red shift in the energy of the PL peak, which is known to be primarily due to thermally activated carrier migration from smaller to larger QDs [12,16]. As presented in Fig.…”

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

“…(iii) High-T range (220-300 K), where the observed decrease of s d is attributed to thermionic losses. 28 The observed increase in s d in the mid-T range is characterized by an activation energy between 20 and 80 meV, as 194306 (2013) in other similar nanostructures, 41,42 InAs/GaAs selfassembled QDs 43,44 and quantum ring nanostructures. 45,46 The origin of this behavior has been attributed to a thermally induced population of dark excitons; 44,45 where transitions p e -s e (or p h -s h ), initially forbidden, becomes allowed due to thermal transfer.…”