Mott transition from a diluted exciton gas to a dense electron-hole plasma in a single V-shaped quantum wire

Abstract

We report on the study of many-body interactions in a single high-quality V-shaped quantum wire by means of continuous and time-resolved microphotoluminescence. The transition from a weakly interacting exciton gas when the carrier density n is less than 105 cm-1 (i.e., naX<0.1, with aX the exciton Bohr radius) to a dense electron-hole plasma (n>106 cm-1, i.e., naX>1) is systematically followed in the system as the carrier density is increased. We show that this transition occurs gradually: the free carriers first coexist with excitons for naX>0.1; then the electron-hole plasma becomes degenerate at naX=0.8. We also show that the nonlinear effects are strongly related to the kind of disorder and localization properties in the structure especially in the low-density regim

Photoluminescence dynamics in GaAs along an optically induced Mott transition

“…Figure 5͑a͒ shows PL spectra at a lattice temperature of 30 K, obtained 60 ps after the arrival of the excitation pulse, for different carrier densities ranging from 0.75ϫ 10 15 cm −3 up to 390ϫ 10 15 cm −3 . 22 Our observations are similar to those reported by Guillet et al in quantum wires, 23 although the redshift is absent in their case probably due to a different weight of the band gap renormalization and Moss-Burstein shift contributions in one dimensional systems as compared with those in bulk materials. 5͑b͒.…”

Controlling the charge environment of single quantum dots in a photonic-crystal cavity

“…12 We instead propose that the off-resonant cavity peak is pumped by a spectrally wide emission ͑to be referred to as "background"͒ due to radiative recombination of QD ͑multi͒excitons, dressed by the Coulomb interactions with carriers in the wetting layer. Such emission, also previously reported, [17][18][19][20] is strongly enhanced by the cavity coupling, as also confirmed by the fast lifetime observed in Fig. 1͑b͒.…”

In As ∕ In P single quantum wire formation and emission at 1.5μm

“…However, for the time being, single quantum wire optical spectroscopy has been restricted mainly to GaAs/ AlGaAs nanostructures emitting on the visible range. The best examples are cleaved edge overgrown T-shaped QWRs, 15,16 V-grooved QWRs grown on nonplanar substrates, 17,18 and recently reported, vertical QWRs grown on inverted tetrahedral pyramids etched away on GaAs substrates. 19 By using in situ accumulated stress measurements, the initial phases of the self-assembling process can be monitored during solid source molecular beam epitaxy of InAs on InP͑001͒.…”

“…They are comparable to similar optical features reported for other semiconductor QWRs based in the GaAs/ AlGaAs heteroepitaxial system. 16,18 Compared with them, the QWRs presented here can be fabricated by a selfassembled process in nominally flat InP͑001͒ substrates, avoiding any prepatterning and/or regrowth steps and making easier their implementation in current photonic and optoelectronic telecommunication devices.…”