A5077661138- Terahertz technology and applications
- Semiconductor Quantum Structures and Devices
- Superconducting and THz Device Technology
- Photonic and Optical Devices
- Semiconductor materials and interfaces
- Semiconductor Lasers and Optical Devices
- Spectroscopy and Laser Applications
- Millimeter-Wave Propagation and Modeling
- Advanced Semiconductor Detectors and Materials
- Surface and Thin Film Phenomena
- Quantum and electron transport phenomena
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Microwave Engineering and Waveguides
- Hepatitis C virus research
- Silicon Nanostructures and Photoluminescence
- Monoclonal and Polyclonal Antibodies Research
- Systemic Lupus Erythematosus Research
- GaN-based semiconductor devices and materials
- Advanced Electron Microscopy Techniques and Applications
- Advanced Fiber Optic Sensors
- Molecular Junctions and Nanostructures
- Silicon and Solar Cell Technologies
- Gyrotron and Vacuum Electronics Research
- Advanced Chemical Physics Studies
University of the Philippines Diliman
2014-2025
University of the Philippines System
2018
Universidade de Santiago de Compostela
2004
The growth of low-temperature-grown GaAs (LTG-GaAs) on semi-insulating substrate with a 0.2 μm n-GaAs buffer demonstrated enhanced terahertz (THz) emission in reflection and transmission excitation geometries via time-domain spectroscopy. transient photocurrent the sample resulting from ultrafast yielded 215% 165% increase THz emission, respectively, as compared grown an undoped buffer. LTG-GaAs film exhibited significant its built-in field supported by calculations photoreflectance...
We present the use of a "double optical pump" technique in terahertz time-domain emission spectroscopy as an alternative method to investigate lifetime photo-excited carriers semiconductors. Compared commonly employed pump-probe transient photo-reflectance, this non-contact and room temperature characterization allows relative ease achieving alignment. The was implemented evaluate carrier low temperature-grown gallium arsenide (LT-GaAs). values deduced from THz decay curves show good...
The carrier lifetimes and electron mobility values were estimated for 2 μm thick GaAs films grown on Si (100) substrates by means of optical pump terahertz probe (OPTP) technique. GaAs/Si measured epitaxial at different substrate temperatures (TS = 520 °C or TS 630 °C). From x-ray diffraction measurements Raman spectroscopy, the shown to experience minimum strain room temperature, crystal misorientation in (111) (110) direction. With no measureable photoluminescence via OPTP found be ∼20 ∼35...
We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics THz signal. The QDs was grown standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- 910 nm-wavelength were used to distinguish emission from InAs/GaAs matrix respectively. THz-TDS nm revealed intense comparable a bulk...
Semiconductor interfaces are the backbone of modern optoelectronic devices. In terahertz (THz) science, narrow region an interface is crucial in emission process. However, reports on direct correlation THz with local properties remain scarce owing to inherent difficulty using same sample for nanoscale and macroscale studies. this study, we combined scanning tunneling microscopy/spectroscopy (STM/STS) spectroscopy study between a highly n+-doped undoped gallium arsenide (GaAs). Using STS,...
Carrier dynamics and photoconductivity in epitaxial-grown low-temperature GaAs on nominal vicinal Si(1 0 0) substrates ('LT-GaAs/Si') were studied to predict their actual performance as THz photoconductive antenna (PCA) detectors. An optical-pump terahertz-probe technique was used obtain the transmittance, carrier lifetime of two LT-GaAs/Si samples, grown using different growth protocols. The LT-GaAs substrate with a 4° tilt 〈1 1 0〉 has better crystallinity, agreement other reports; while...
Two asymmetric double quantum wells of different coupling strengths (barrier widths) were grown via molecular beam epitaxy, both samples allowing tunneling. Photoluminescence was measured at 10 and 300 K to provide evidence tunneling, barrier dependence, structural uniformity. Carrier dynamics room temperature investigated by optical pump terahertz probe (OPTP) spectroscopy. population decay rates obtained photoconductivity spectra analyzed using the Drude model. This work demonstrates that...
Intense terahertz (THz) emission in high quality GaAs film upon ultrafast excitation is demonstrated. Results showed that grown by molecular beam epitaxy with a thin n-doped buffer can rival existing intense bare semiconductor THz surface emitters. The incorporation of 0.2 µm n-GaAs proved effective enhancing the 281% and 295% reflection transmission time-domain geometries, respectively. was crystallinity or without layer as confirmed from X-ray diffraction Raman scattering. similar...
Abstract We present the implementation of an efficient terahertz (THz) photoconductive antenna (PCA) emitter design that utilizes high mobility carriers in two-dimensional electron gas (2DEG) a modulation-doped heterostructure (MDH). The PCA is fabricated with recessed metal electrodes direct contact 2DEG region MDH. compare performance MDH having contacts on bulk semi-insulating GaAs, low temperature-grown and surface. By recessing contacts, applied bias can effectively accelerate...
GaAs films were grown on Si (100) substrates with a "two-step buffer" growth technique using molecular beam epitaxy, wherein low temperature buffer is at two substrate temperatures prior to the layer. Results of layer different are compared photoluminescence, Raman, and optical-pump terahertz-probe spectroscopy.
Epitaxial low temperature grown GaAs (LT-GaAs) on silicon (LT-GaAs/Si) has the potential for terahertz (THz) photoconductive antenna applications. However, crystalline, optical and electrical properties of heteroepitaxial LT-GaAs/Si can be very different from those semi-insulating substrates (reference). In this study, we investigate an epitaxial sample, compared to a reference under same substrate temperature, with layer thickness. Anti-phase domains some crystal misorientation are present...
Bowtie photoconductive antennas (PCAs) with a 10-μm gap were fabricated on epitaxial grown LT-GaAs layers Silicon substrates (LT-GaAs-on-Si). The samples used distinct growth parameters. performance of the PCAs as terahertz detectors are presented in this report.
Using a combination of scanning tunneling microscopy (STM) and spectroscopy with density functional theory calculations, the electronic properties subsurface arsenic antisite defect (As Ga ) are unambiguously delineated from those surrounding As atoms in undoped gallium arsenide (GaAs) lattice atomic precision. In GaAs(110) surface located at second layer (2‐As ), it is found that midgap state induced by 2‐As manifests as bright contrast As bond site. Furthermore, shown STM images taken...
We investigate strain effects on the ultrafast carrier dynamics and transport of gallium arsenide films silicon (GaAs/Si) magnesium oxide (GaAs/MgO) substrates using temperature-dependent photoluminescence (PL) terahertz time-domain spectroscopy (THz-TDS) from 11 K - 300 K. The PL shows that GaAs/Si GaAs/MgO samples are under tensile compressive at low temperature, respectively. THz emission does not show significant differences with bulk GaAs, while an order-of-magnitude decrease...