Optical properties of as-grown and annealed InAs quantum dots on InGaAs cross-hatch patterns

Abstract

InAs quantum dots (QDs) grown on InGaAs cross-hatch pattern (CHP) by molecular beam epitaxy are characterized by photoluminescence (PL) at 20 K. In contrast to QDs grown on flat GaAs substrates, those grown on CHPs exhibit rich optical features which comprise as many as five ground-state emissions from [1-10]- and [110]-aligned QDs, two wetting layers (WLs), and the CHP. When subject to in situ annealing at 700°C, the PL signals rapidly degrades due to the deterioration of the CHP which sets the upper limit of overgrowth temperature. Ex situ hydrogen annealing at a much lower temperature of 350°C, however, results in an overall PL intensity increase with a significant narrowing and a small blueshift of the high-energy WL emission due to hydrogen bonding which neutralizes defects and relieves associated strains.

Excitation transfer in stacked quantum dot chains

“…Certain growth conditions can extend the wavelength to the 1.3-1.55 μm telecom window [18] or lead to bimodal or multimodal size distributions with multiple PL peaks [19][20][21], while random distribution remains. In contrast, InAs QDs grown on CHPs are guided, forming chains along the orthogonal [110] and [11 ¯0] directions, each direction with its own size, size distribution, and wetting layer (WL) due to the asymmetry of the underlying dislocations [22]. The formation of QDs along the orthogonal dislocation chains has been established by planview transmission electron microscopy (TEM) [23], whereas vertical correlation of QDs with 10 nm GaAs spacer has been confirmed by cross-sectional TEM [24].…”

“…It has long been known that the underlying InGaAs/GaAs CHPs are asymmetric: the [11 ¯0] stripes nucleate earlier, have greater density, and result in surface steps which are taller than the [110] stripes [28]. The asymmetry is transferred to the overgrown layers, resulting in QDs along the [11 ¯0] direction forming slightly earlier and are thus taller and emit at a lower energy than those along the orthogonal [110] direction [22,27,29]. The microscopic images in figures 1(c)-(d) provide a clear visual evidence of QD luminescence decorating the [11 ¯0] and [110] stripes, at slightly different energies.…”

Optical and electrical characteristics of high‐efficiency InGaP/InGaAs/Ge triple‐junction solar cell incorporated with InGaAs/GaAs QD layers in the middle cell

“…3.1. X-ray diffraction and photoluminescence characterization of InGaAs/GaAs QD structure [15][16][17][18][19][20][21] The epitaxy quality of cells with and without layers of QDs was examined by DC-XRD measurement, as shown in Figure 2. Satellite peaks originating from the InGaAs/GaAs QD structure were clearly observed in the XRD curves.…”

Epitaxial nanowire formation in metamorphic GaAs/GaPAs short-period superlattices

“…[8][9][10] But few reports on the use of metamorphic grades for epitaxial nanostructures, which may offer solutions to next-generation device concepts, 11 are available. [12][13][14] Lifting the restriction of lattice-matching allows, for example, access to particular bandgaps or band offsets, while tailoring the compositional grade enables independent adjustment of strain to affect nanostructure formation. Lattice mismatch is critical to many self-assembled, epitaxial nanostructures, as it is the coherency strain inherent to these systems that often drives organization into non-planar morphology, such as in Stranski-Krastanov growth mode, in which formation of a 2-D wetting layer precedes the development of 3-D islands.…”