Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires

Abstract

We probe and control the optical properties of emission centers forming in radial heterostructure GaAs-Al 0.3 Ga 0.7 As nanowires and show that these emitters, located in Al 0.3 Ga 0.7 As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy and occupancy state on a nanosecond timescale. In the spectral oscillations we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, different emission lines of a single emission center exhibit pronounced anti-correlated intensity oscillations during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the emission center to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mechanism. These simulation results quantitatively reproduce the observed switching and show that in our systems these emission centers are spatially separated from the continuum by > 10.5 nm.

Radio frequency occupancy state control of a single nanowire quantum dot

“…Furthermore, the φ-dependency of h density is anticorrelated to that of e providing further evidence for the the preferential formation of negatively charged excitons. The emission lines similar to those reported by Heiss et al in [33] exhibit also a characteristic SAW-response [30]. This, however, features characteristic differences to that reported here since both the emission center and the driving mechanism are of different nature: (i) In Ref.…”

“…The emission of the 2 nm QW extends over a ∼ 100 meV wide energy band centered at E QW = 1.7 eV. This emission is not observed for a reference sample without a radial QW, which excludes other types of emitter systems [31,33,30] as its origin. The large spread of the emission energy is from the (i) the small nominal thickness and (ii) the fact that growth occurs on the [110]-type facet of a NW.…”

“…At such low acoustic amplitudes the contribution of SAW-induced lateral electric fields are weak [48] and the observed spectral shift is dominated by the strain contribution. [49,30] The extracted relative spectral tuning ∆E strain of 1X 0 and 1X − are plotted as a function of φ in Fig. 2 (b).…”

“…Taken together, the maximum (minimum) emission energies are observed for the value of φ at which p is maximum positive (negative). For the crystal cut of our LiNbO 3 substrate we can derive the φ-dependence of the SAW-induced modulation of the conduction (CB) and valence band (VB) within the GaAs NW using finite element modeling (FEM) [30] which is shown in Fig. 2(c) for times t = 0 (i.e.…”

“…Radio frequency surface acoustic waves (SAWs) represent a particularly attractive and powerful tool to probe and dynamically control charge excitations in semiconductor heterostructure including Quantum Hall systems [12,13,14], charge transport in oneand two-dimensional electron channels [15,16], transport of charges [17,18,19], spins [20] or dipolar excitons [21] and precisely timed carrier injection into QDs for low-jitter single photon emission [22,23,24,25]. Recently, these concepts have been transferred to intrinsic nanowires (NWs) [26] and nanotubes [27] and NWs containing complex radial and axial heterostructures [28,29,30].…”