Epitaxial growth of lateral quantum dot molecules

Abstract

We present an overview and a comparison between three different methods of creating low density lateral In(Ga)As quantum dot molecules (QDMs) embedded in a GaAs matrix. Each of them is based on the use of nanoholes to control the dot nucleation site and generate the QDMs. The three methods used to create suitable nanoholes are: (1) In situ excess gallium droplet etching, where the nanohole shape is modified by overgrowth of a thin GaAs buffer to give QDM nucleation. (2) Ex situ electronbeam lithographic patterning and wet-etching, where the patterned nanohole size is critical for formation of QDMs. (3) In situ strain-selective etching of buried InAs quantum dots by AsBr 3 . The mechanisms of QDM formation, dependence on growth parameters, advantages and disadvantages of each technique and future challenges are discussed. . However, for quantum computation applications, interacting quantum systems are required [6]. One possible way to achieve this is to use the so-called 'quantum dot molecules' (QDMs).The most convenient method to realise optically active QDMs [7] is to take advantage of the vertical ordering which occurs between stacked layers of dots [8]. The quantum states in the two dots can be coupled by choosing a suitable spacer layer thickness and by applying an electric field to compensate differences in the dot sizes [9,10]. However, the lateral geometry is attractive due to the possibility of selectively contacting the single molecule and modulating the coupling strength between the dots [11][12][13][14].There are several ways to modify the substrate morphology in order to guide the growth of lateral QDMs. For example, QDMs have been grown on the facet edges of mounds [15,16], at the corners of pyramidal structures formed during selective area epitaxy [17] or on the edges and the bottom of nanoholes [11,12,[18][19][20][21][22].

Influence of Ga coverage on the sizes of GaAs quantum dash pairs grown by high temperature droplet epitaxy

“…As a versatile growth method, DE could find application in creating novel three‐dimensional nanostructures for future electronic and optoelectronic devices. Among these nanostructures, QD molecules (QDMs) have received much attention due to their potential applications in quantum computing 5. The simplest and most investigated QDM is coupled QDs 6.…”

Fine structure of bright and dark excitons in asymmetric droplet epitaxy GaAs/AlGaAs quantum dots

“…This technique leads to highly uniform [16] and isotropic GaAs QDs [17] showing very small bright-bright exciton splitting [18]. This nanohole-infilling approach can also be associated with nanopatterned substrate to control the QDs position and realize QDs arrays [19,20]. Moreover, in these filled nanohole QDs, very recent studies have evidenced the opportunity to observe DE states [21,22] to control the DE decay rate and heavy-hole (HH)-light-hole (LH) mixing via strain or electric field [23].…”

Three-electron dynamics of the interparticle Coulombic decay with two-dimensional continuum confinement

“…39,40 Just recently, the ICD rate equation was also confirmed in electron dynamics calculation in two-electron systems with a two-dimensional electronic continuum. 48,51 The respective potentials correspond to laterally-arranged self-assembled [52][53][54] or electrostatically confined QDs. 55 There, the dynamics rates showed much less pronounced oscillations with parameter variations in comparison to the analytical monotonic rate as function of the respective parameter, where the parameter considered so far was the inter-QD distance.…”