Investigation into the InAs/GaAs quantum dot material epitaxially grown on silicon for O band lasers

InAs/GaAs quantum dot (QD) lasers were grown on silicon substrates using a thin Ge buffer and three-step growth method in the molecular beam epitaxy (MBE) system. In addition, strained superlattices were used to prevent threading dislocations from propagating to the active region of the laser. The as-grown material quality was characterized by the transmission electron microscope, scanning electron microscope, X-ray diffraction, atomic force microscope, and photoluminescence spectroscopy. The results show that a high-quality GaAs buffer with few dislocations was obtained by the growth scheme we developed. A broad-area edge-emitting laser was also fabricated. The O-band laser exhibited a threshold current density of 540 A/cm2 at room temperature under continuous wave conditions. This work demonstrates the potential of large-scale and low-cost manufacturing of the O-band InAs/GaAs quantum dot lasers on silicon substrates.

Modeling electron transfer from the barrier in InAs/GaAs quantum dot-well structure

We study single electron tunnelling from the barrier in the binary InAs/GaAs quantum structure including quantum well (QW) and quantum dot (QD). The tunneling is described in the terms of localized/delocalized states and their spectral distribution. The modeling is performed by using the phenomenological efective potential approach for InAs/GaAs heterostructures. The results for the two and three-dimensional models are presented. We focus on the efect of QD-QW geometry variations. The relation to the PL experiments is shown.

Symmetric Excitons in an (001)-Based InAs/GaAs Quantum Dot Near Si Dopant for Photon-Pair Entanglement

The sacrificed-QD-layer method can well control the indium deposition amount to grow InAs quantum dots (QDs) with isotropic geometry. Individual Si dopant above an (001)-based InAs QD proves a new method to build a local electric field to reduce fine structure splitting (FSS = X1−X2) and show D3h symmetric excitons. The lowest FSS obtained is 3.9 μeV with the lowest energy X state (LX) anticlockwise rotate from [1−10] (i.e., zero FSS will be crossed in a proper field). The lateral field projection induces a large eh separation and various FSS, LX, and emission intensity polarization. The lateral field along [1−10] breaks the X1–X2 wavefunction degeneracy for independent HH and VV cascade emissions with robust polarization correlation. With FSS ~4 μeV and T1 ~0.3 ns fastened in a distributed Bragg reflector cavity, polarization-resolved XX–X cross-correlations show fidelity ~0.55 to a maximal entangled state |HH> + |VV>. A higher fidelity and zero FSS will be obtained in the hybrid QD structure with a junction field integrated to tune the FSS and a sub-bandgap excitation to avoid influences from electrons in the barrier.

Optical Properties from a Single GaAs Quantum Dot Structure

We observed exciton and biexciton states in a single GaAs quantum dot at 4 K using micro pho-toluminescence system and investigated power dependent photoluminescence measurements to identify both exciton and biexciton states. The biexciton and exciton states showed quadratic (a~2.2) and linear (a~0.95) increasing power factor, respectively. The large energy difference (~0.2 meV) from exciton states for the perpendicular polarization was observed.