Chirped InGaAs quantum dot molecules for broadband applications

Abstract

Lateral InGaAs quantum dot molecules (QDMs) formed by partial-cap and regrowth technique exhibit two ground-state (GS) peaks controllable via the thicknesses of InAs seed quantum dots (x), GaAs cap (y), and InAs regrowth (z). By adjusting x/y/z in a stacked QDM bilayer, the GS peaks from the two layers can be offset to straddle, stagger, or join up with each other, resulting in multi-GS or broadband spectra. A non-optimized QDM bilayer with a 170-meV full-width at half-maximum is demonstrated. The temperature dependencies of the emission peak energies and intensities from the chirped QDM bilayers are well explained by Varshni's equation and thermal activation of carriers out of constituent quantum dots.

Excitation transfer in stacked quantum dot chains

“…Understanding the coupling nature of vertically stacked QD structures is of fundamental importance to the operation and optimization of QD-based devices such as memory [4], lasers [5] and solar cells [6,7]. Though useful, coupling is not always necessary or desired, particularly for broadband applications which benefit from the superposition of different wavelengths from individual QD layers [8]. If present, electronic coupling results in the lowering of the excitonic ground-state (GS) energy, and consequently a redshift of photoluminescent peak [3,9].…”

Cross-correlation spectra in interacting quantum dot systems

“…where H (i) is the Hamiltonian of the i-th QD and S (i) denotes its electron spin operator; i runs over all QDs of the ensemble. Note, in this general form, H also applies for QD molecules 35 , QD chains 36 or QD super-lattices 37 , whereas the specific geometry of the QDs is encoded in the interaction matrix J ij .…”