Tunnel coupling in an ensemble of vertically aligned quantum dots at room temperature

Abstract

We report unambiguous observation of the formation of mixed electronic states in an ensemble of selfassembled vertically aligned quantum dots at room temperature. Three closely spaced layers containing stacked In͑Ga͒As/GaAs quantum dots are placed in the active region of a two-section semiconductor device, and investigations of the quantum-dot optical properties at different applied electric fields are carried out by means of differential-absorption spectroscopy. A simple semianalytical model, which describes absorption of two layers of coupled quantum dots with an account of the size dispersion, is developed. A comparison between our experimental and theoretical results allows clear attribution of the observed low-photon-energy field-dependent spectral features to the four mixed optical transitions due to the two upper quantum-dot layers. Interpretation of the experimental results reveals an anticrossing of spatially direct and indirect transitions characterized by the energy splitting of approximately 30 meV.

Switching between the mode-locking and Q-switching modes in two-section QW lasers upon a change in the absorber properties due to the Stark effect

“…2). To explain this effect, we measured the absorption spectra at various reverse biases by integrated-absorption spectroscopy [10]. Figure 3 shows the absorption and lasing spectra at voltages applied to the absorber section of 6.9 and 9 V, at which the PQS and PML modes, respectively, operate.…”

Room temperature passive mode-locked laser based on InAs/GaAs quantum-dot superlattice

“…Absorption measurements were provided as described in [8,9] using this device. The experimental setup is shown on Figure 2b,c.…”

Correlated Roles of Temperature and Dimensionality for Multiple Exciton Generation and Electronic Structures in Quantum Dot Superlattices

“…We especially examine the QDSLs which exhibit the short-range quantum resonance among component QDs. The short-range quantum resonance, which appears only in the interior nano space smaller than 2 nm among component QDs of diameter smaller than 4 nm, is not a simple overlap of wave functions between quantum well potentials [50][51][52][53][54] but rather orbitaldependent delocalization into adjoining QDs accompanied by the orbital deformation. 33,39,55 We will report the temperature dependence of not only static but also time-dependent dynamical quantities to characterize such QDSLs of each dimensionality, identifying the correlated roles of the dimensionality and temperature intrinsic to each QDSL.…”

“…We especially examine the QDSLs that exhibit a short-range quantum resonance among component QDs. The short-range quantum resonance, which appears only in the interior nanospace smaller than 2 nm among component QDs of diameter smaller than 4 nm, is not a simple overlap of wave functions between quantum well potentials − but rather an orbital-dependent delocalization into adjoining QDs accompanied by orbital deformation. ,, We will report the temperature dependence of not only static but also time-dependent dynamical quantities to characterize such QDSLs of each dimensionality, identifying the correlated roles of the dimensionality and temperature intrinsic to each QDSL. The insights we obtained here are crucial not only for understanding the physical mechanisms that govern photoexcited processes occurring in the QDSLs but also for designing compact and functionalized optoelectronic and photovoltaic devices like photodetectors and solar cells by controllably engineering their physical properties.…”