A5090188122- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Advanced Fiber Optic Sensors
- Semiconductor Quantum Structures and Devices
- Nanowire Synthesis and Applications
- Photonic Crystals and Applications
- Mechanical and Optical Resonators
- Advanced Fiber Laser Technologies
- Graphene research and applications
- Semiconductor materials and devices
- Advanced Photonic Communication Systems
- Neural Networks and Reservoir Computing
- Plasmonic and Surface Plasmon Research
- Silicon Nanostructures and Photoluminescence
- 2D Materials and Applications
- Advanced MEMS and NEMS Technologies
- Thin-Film Transistor Technologies
- Diamond and Carbon-based Materials Research
- Advancements in Semiconductor Devices and Circuit Design
- Quantum optics and atomic interactions
- Semiconductor materials and interfaces
- Quantum and electron transport phenomena
- Topological Materials and Phenomena
- Ocular and Laser Science Research
- Cold Atom Physics and Bose-Einstein Condensates
Korea Advanced Institute of Science and Technology
2024-2025
Nanyang Technological University
2018-2024
Yonsei University
2023
Inha University
2015-2018
Stanford University
2011-2015
Seoul National University
1996
(Si)GeSn semiconductors are finally coming of age after a long gestation period. The demonstration device quality epi-layers and quantum-engineered heterostructures has meant that tunable all-group IV Si-integrated infrared photonics is now real possibility. Notwithstanding the recent exciting developments in materials devices, this family still facing serious limitations need to be addressed enable reliable scalable applications. main outstanding challenges include difficulty grow high...
Infrared machine vision system for object perception and recognition is becoming increasingly important in the Internet of Things era. However, current suffers from bulkiness inefficiency as compared to human retina with intelligent compact neural architecture. Here, we present a retina-inspired mid-infrared (MIR) optoelectronic device based on two-dimensional (2D) heterostructure simultaneous data encoding. A single can perceive illumination intensity MIR stimulus signal, while encoding...
Abstract The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to realization fully functional photonic-integrated circuits. Despite several years progress, however, all reported date exhibit impractically high thresholds owing their unfavourable bandstructures. Highly strained germanium with its fundamentally altered bandstructure has emerged as a potential low-threshold gain medium, but there yet be successful demonstration lasing from this...
We report uniaxial tensile strains up to 5.7% along 〈100〉 in suspended germanium (Ge) wires on a silicon substrate, measured using Raman spectroscopy. This strain is sufficient make Ge direct bandgap semiconductor. Theoretical calculations show that significant fraction of electrons remain the indirect conduction valley despite due much larger density states; however, recombination can nevertheless be dominated by radiative transitions if defects are minimized. then calculate theoretical...
This work presents a novel method to introduce sustainable biaxial tensile strain larger than 1% in thin Ge membrane using stressor layer integrated on Si substrate. Raman spectroscopy confirms 1.13% and photoluminescence shows direct band gap reduction of 100meV with enhanced light emission efficiency. Simulation results predict that combination 1.1% heavy n(+) doping reduces the required injected carrier density for population inversion by over factor 60. We also present first highly...
Semiconductor heterostructures play a vital role in photonics and electronics. They are typically realized by growing layers of different materials, complicating fabrication limiting the number unique heterojunctions on wafer. In this Letter, we present single-material nanowires which behave exactly like traditional heterostructures. These pseudoheterostructures have electronic band profiles that custom-designed at nanoscale strain engineering. Since profile depends only nanowire geometry...
Abstract Despite the potential of graphene for building a variety quantum photonic devices, its centrosymmetric nature forbids observation second harmonic generation (SHG) developing second-order nonlinear devices. To activate SHG in graphene, extensive research efforts have been directed towards disrupting graphene’s inversion symmetry using external stimuli like electric fields. However, these methods fail to engineer lattice symmetry, which is root cause forbidden SHG. Here, we harness...
Two-dimensional (2D) materials have emerged as promising candidates for next-generation integrated single-photon emitters (SPEs). However, significant variability in the emission energies presents a major challenge producing identical single photons from different 2D SPEs, which may become crucial practical quantum applications. Although various approaches to dynamically tuning of SPEs been developed address issue, solution matching multiple individual is still scarce. In this work, we...
We provide a theoretical analysis of the relative merits tensile strain and n-type doping as approaches to realizing an efficient low-power germanium laser. Ultimately, offers threshold reductions over 200x, significant improvements in slope efficiency compared with recently demonstrated 0.25% strained electrically pumped In contrast, fundamentally limited benefits, too much is harmful. Moreover, we predict that reduces optimal value experimentally has already reached its fundamental limit....
In this paper, a theoretical analysis of unstrained GeSn alloys as laser gain medium was performed. Using the empirical pseudopotential method, band structure simulated and verified against experimental data. This model shows that becomes direct bandgap with 6.55% Sn concentration. The optical 0-10% concentration calculated different n-type doping concentrations injection levels. It is shown theoretically adding greatly increases differential owing to reduction energy between indirect...
We demonstrate room-temperature electroluminescence (EL) from light-emitting diodes (LED) on highly strained germanium (Ge) membranes. An external stressor technique was employed to introduce a 0.76% bi-axial tensile strain in the active region of vertical PN junction. Electrical measurements show an on-off ratio increase one order magnitude membrane LEDs compared bulk. The EL spectrum Ge LED shows 100nm redshift center wavelength because strain-induced direct band gap reduction. Finally,...
A silicon-compatible light source is the final missing piece for completing high-speed, low-power on-chip optical interconnects. In this paper, we present a germanium-based emitter that encompasses all aspects of potential low-threshold lasers: highly strained germanium gain medium, strain-induced pseudo-heterostructure, and high-Q cavity. Our emitting structure presents greatly enhanced photoluminescence into cavity modes with measured quality factors up to 2,000. The emission wavelength...
The creation of pseudo-magnetic fields in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be unattainable with laboratory superconducting magnets. Scanning tunneling spectroscopy experiments have successfully measured the pseudo-Landau levels and proved existence various systems. These giant observed highly deformed can substantially alter optical properties beyond level feasible an external magnetic field, but experimental...
Abstract Plasmonics on metal-dielectric interfaces was widely seen as the main route for miniaturization of components and interconnect photonic circuits. However recently, ultra-confined surface phonon-polaritonics in high-index chalcogenide films nanometric thickness has emerged an important alternative to plasmonics. Here, using mid-IR near-field imaging we demonstrate tunable phonon-polaritons CMOS-compatible few-nm thick germanium silicon carbide. We show that Ge-SiC resonators with...
Abstract GeSn alloys are promising candidates for complementary metal‐oxide‐semiconductor‐compatible, tunable lasers. Relaxation of residual compressive strain in epitaxial has recently shown promise improving the lasing performance. However, suspended device configuration that is thus far introduced to relax destined limit heat dissipation, hindering Herein demonstrated strain‐free microdisk laser devices fully released on Si outperform canonical devices. This approach allows simultaneously...
GeSn alloys have been regarded as a potential lasing material for complementary metal–oxide–semiconductor-compatible light source. Despite their remarkable progress, all lasers reported to date large device footprints and active areas, which prevent the realization of densely integrated on-chip operating at low power consumption. Here, we present 1D photonic crystal nanobeam with very small footprint 7 μm2 compact area ∼1.2 on high-quality GeSn-on-insulator substrate. We also report that...
Nanowires are promising platforms for realizing ultra-compact light sources photonic integrated circuits. In contrast to impressive progress on confinement and stimulated emission in III-V II-VI semiconductor nanowires, there has been no experimental demonstration showing the potential achieve strong cavity effects a bottom-up grown single group-IV nanowire, which is prerequisite silicon-compatible infrared nanolasers. Herein, we address this limitation present an observation of...
Vacancy defects in germanium (Ge) adversely impact the electrical performance of Ge based metal-oxide-semiconductor field-effect transistor (MOSFET) several ways. They behave as an acceptor site, thereby deactivating n-type dopants source/drain region. can also increase substrate leakage currents and carrier lifetime channel In this paper, we characterize verify behavior vacancy using spreading resistance profiling (SRP). Effect thermal annealing on concentration is studied. Finally,...
In this paper, we present a comprehensive study of carrier statistics in germanium with high uniaxial strain along the [100] direction. Several types PL experiments were conducted to investigate polarization-, temperature- and excitation-dependent under various amounts strain. With ability clearly resolve multiple photoluminescence peaks originating from strain-induced valence band splitting, experimentally observed strongly polarized light emission direct gap transitions. Our also confirm...
We extend the previous 30-band $k$$\cdot$$p$ model effectively employed for relaxed Ge$_{1-x}$Sn$_{x}$ alloy to case of strained alloy. The strain-relevant parameters are obtained by using linear interpolation between values single crystal Ge and Sn that from literatures optimizations. specially investigate dependence band-gap at $L$-valley $\Gamma$-valley with different composition under uniaxial biaxial strain along [100], [110] [111] directions. good agreement our theoretical predictions...
Despite its advantages of scalable process and cost-effectiveness, nanoimprinting faces challenges with imprinting hard materials (e.g., crystalline metals) at low/room temperatures, fabricating complex nanostructures rapidly heterojunctions metal oxide). Herein, we report a room temperature ultrasonic technique (named nanojackhammer) to address these challenges. Nanojackhammer capitalizes on the concentration energy flow nanoscale shape bulk into nanostructures. Working temperature,...
The ability to precisely control moiré patterns in two-dimensional materials has enabled the realization of unprecedented physical phenomena including Mott insulators, unconventional superconductivity, and quantum emission. Along with twist angle, application independent strain each layer stacked materials-termed heterostrain-has become a powerful means manipulate potential landscapes. Recent experimental studies have demonstrated possibility continuously tuning angle resulting properties....
Two-dimensional (2D) materials-based photodetectors in the infrared range hold key to enabling a wide of optoelectronics applications including imaging and optical communications. While there exist 2D materials with narrow bandgap sensitive photons, two-photon absorption (TPA) process can also enable photodetection well-established large bandgaps such as WSe2 MoS2. However, most TPA suffer from low responsivity, preventing this method being widely adopted for photodetection. Herein, we...
Complementary metal oxide semiconductor-compatible short- and midwave infrared emitters are highly coveted for the monolithic integration of silicon-based photonic electronic integrated circuits to serve a myriad applications in sensing communication. In this regard, group IV germanium–tin (GeSn) material epitaxially grown on silicon (Si) emerges as promising platform implement tunable light emitters. Indeed, upon increasing Sn content, bandgap GeSn narrows becomes direct, making system...
We report improved minority carrier lifetimes in n-type-doped and tensile-strained germanium by measuring direct bandgap photoluminescence from germanium-on-insulator substrates with various levels of defect density. first describe a method to fabricate high-quality substrate employing wafer bonding chemical-mechanical polishing. Raman spectroscopy measurement was performed assess the purity transferred layer on an insulator. Using time-resolved decay measurement, we observe that can be over...