E-Band InAs Quantum Dot Micro-Disk Laser with Metamorphic InGaAs Layers Grown on GaAs/Si (001) Substrate.

The direct growth of III-V quantum dot (QD) lasers on silicon substrate has been rapidly developing over the past decade and has been recognized as a promising method for achieving on-chip light sources in photonic integrated circuits (PICs). Up to date, O- and C/L-bands InAs QD lasers on Si have been extensively investigated, but as an extended telecommunication wavelength, the E-band QD lasers directly grown on Si substrates are not available yet. Here, we demonstrate the first E-band (1365 nm) InAs QD micro-disk lasers epitaxially grown on Si (001) substrates by using a III-V/IV hybrid dual-chamber molecular beam epitaxy (MBE) system. The micro-disk laser device on Si was characterized with an optical threshold power of 0.424 mW and quality factor (Q) of 1727.2 at 200 K. The results presented here indicate a path to on-chip silicon photonic telecom-transmitters.

Strain-induced ordered Ge(Si) hut wires on patterned Si (001) substrates.

Ge/Si nanowires are predicted to be a promising platform for spin and even topological qubits. While for large-scale integration of these devices, nanowires with fully controlled positions and arrangements are a prerequisite. Here, we have reported ordered Ge hut wires by multilayer heteroepitaxy on patterned Si (001) substrates. Self-assembled GeSi hut wire arrays are orderly grown inside patterned trenches with post growth surface flatness. Such embedded GeSi wires induce tensile strain on the Si surface, which results in preferential nucleation of Ge nanostructures. Ordered Ge nano-dashes, disconnected wires and continuous wires are obtained correspondingly by tuning the growth conditions. These site-controlled Ge nanowires on a flattened surface lead to the ease of fabrication and large-scale integration of nanowire quantum devices.

Atomically Thin Delta-Doping of Self-Assembled Molecular Monolayers by Flash Lamp Annealing for Si-Based Deep UV Photodiodes.

Delta doping (δ-doping) can find a wide range of applications in advanced metal oxide semiconductor field effect transistors, deep UV photodetectors, quantum devices, and others. In this work, we formed a δ-doping layer in silicon by employing flash lamp annealing to treat the PCl3 monolayers grafted on silicon surfaces. The δ-doping layer is atomically thin (<1 nm). Low-temperature Hall measurements show that the δ-doping layer is in a metallic state and exhibits a weak localization phenomenon, implying that a two-dimensional electron gas is formed. When we form such an n-type δ-doping layer on a highly doped p-type Si substrate, a highly sensitive solar-blind UV photodetector is created, which traditionally was only possible by using wide band gap semiconductors such as gallium nitride (GaN) or silicon carbide (SiC).

Phosphorus-free 1.5 µm InAs quantum-dot microdisk lasers on metamorphic InGaAs/SOI platform.

III-V semiconductor lasers epitaxially grown on silicon, especially on a silicon-on-insulator (SOI) platform, have been considered one of the most promising approaches to realize an integrated light source for silicon photonics. Although notable achievements have been reported on InP-based 1.5 µm III-V semiconductor lasers directly grown on silicon substrates, phosphorus-free 1.5 µm InAs quantum dot (QD) lasers on both silicon and SOI platforms are still uncharted territory. In this work, we demonstrate, to the best of our knowledge, the first phosphorus-free InAs QD microdisk laser epitaxially grown on SOI substrate emitting at the telecommunications S-band by growing metamorphic InAs/InGaAs QDs on (111)-faceted SOI hollow structures. The lasing threshold power for a seven-layer InAs QD microdisk laser with a diameter of 4 µm is measured as 234 µW at 200 K. For comparison, identical microdisk lasers grown on GaAs substrate are also characterized. The results obtained pave the way for an on-chip 1.5 µm light source for long-haul telecommunications.

Site-Controlled Uniform Ge/Si Hut Wires with Electrically Tunable Spin-Orbit Coupling.

Semiconductor nanowires have been playing a crucial role in the development of nanoscale devices for the realization of spin qubits, Majorana fermions, single photon emitters, nanoprocessors, etc. The monolithic growth of site-controlled nanowires is a prerequisite toward the next generation of devices that will require addressability and scalability. Here, combining top-down nanofabrication and bottom-up self-assembly, the growth of Ge wires on prepatterned Si (001) substrates with controllable position, distance, length, and structure is reported. This is achieved by a novel growth process that uses a SiGe strain-relaxation template and can be potentially generalized to other material combinations. Transport measurements show an electrically tunable spin-orbit coupling, with a spin-orbit length similar to that of III-V materials. Also, charge sensing between quantum dots in closely spaced wires is observed, which underlines their potential for the realization of advanced quantum devices. The reported results open a path toward scalable qubit devices using nanowires on silicon.

1310 nm InAs quantum-dot microdisk lasers on SOI by hybrid epitaxy.

Direct epitaxial growth of O-band InAs/GaAs quantum-dot laser on Si substrates has been rapidly developing over the past few years. But most of current methodologies are not fully compatible with silicon-on-insulator (SOI) technology, which is the essential platform for silicon photonic devices. By implementing an in situ III-V/Si hybrid growth technique with (111)-faceted Si hollow structures, we demonstrate the first optically pumped InAs/GaAs quantum-dot microdisk laser on SOI substrates grown by molecular beam epitaxy (MBE). The microdisk laser on SOI is characterized with threshold pump power as low as 0.39 mW and a Q factor of 3900 at room temperature. Additionally, the compared device performance of InAs quantum-dot microdisk lasers on GaAs, Si (001) and SOI are simultaneously studied with identical epi-structures.