Rafael Jaculbia

Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures

We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.

Terahertz emission from GaAs-AlGaAs core-shell nanowires on Si (100) substrate: Effects of applied magnetic field and excitation wavelength

Terahertz (THz) emission from GaAs-AlGaAs core-shell nanowires (CSNW) on silicon (100) substrates was investigated using THz time-domain spectroscopy. The applied magnetic field polarity dependence strongly suggests that THz emission originated from photo-carriers in the CSNWs. Optical excitation of the GaAs-AlGaAs core-shell yielded a wider THz emission bandwidth compared with that of just the GaAs core material. This result is currently attributed to faster carrier lifetimes in the AlGaAs shell. The THz emission spectral data are supported by time-resolved photoluminescence studies.

Photocarrier Transport and Carrier Recombination Efficiency in Vertically Aligned Si Nanowire Arrays Synthesized Via Metal-Assisted Chemical Etching

The carrier dynamics and recombination characteristics of vertically aligned silicon nanowires are investigated using terahertz emission and photoluminescence spectroscopy, respectively. It is observed that the presence of pores on the walls in two-step-synthesized silicon nanowires greatly affects the carrier dynamics, compared with nanowires synthesized using a one-step process. These pores become efficient carrier recombination sites wherein carriers are collected upon photoexcitation. Additionally, pores effectively diminish the surface electric field thereby inhibiting the terahertz emission. Finally, nanowire-length-dependent terahertz emission is observed only for the one-step-synthesized nanowires whereas the two-step-synthesized nanowire samples exhibited length dependence of their photoluminescence intensity.

Transitions of epitaxially lifted-off bulk GaAs and GaAs/AlGaAs quantum well under thermal-induced compressive and tensile strain

Low temperature photoluminescence and reflectance measurements on epitaxially lifted-off (ELO) bulk GaAs and GaAs/AlGaAs multiple quantum wells (MQWs) bonded to Si and MgO substrates are reported. Photoluminescence measurements indicate no strain at room temperature for the ELO bulk GaAs film but show biaxial strain at 10 K. Si-bonded films undergo tensile strain, while films with MgO host substrates experience compressive strain. Reflectance measurements at 10 K show that light hole band is closer to the conduction band for the tensile strained film. In GaAs MQW ELO films, the separation of the heavy hole and light hole band is reduced in tensile strained films by 4.7 meV, corresponding to a strain e=−0.7±0.05×10−3 and stress X=0.9±0.05 kbar (90±5 MPa). For compressively strained films, this separation is enhanced by 3.9 meV, equivalent to a strain e=0.6±0.05×10−3 and X=0.8±0.05×10−3 kbar (80±5 MPa). The findings demonstrate that ELO is an effective technique to introduce tensile and compressive strain i...

Surface effect of n-GaAs cap on the THz emission in LT-GaAs

The deposition of n-GaAs cap on low-temperature GaAs (LT-GaAs) improved the THz emission of LT-GaAs grown at a much lower temperature (<

Terahertz emission from aluminum-doped ZnO–nGaAs heterostructure investigated using reflection-mode terahertz time-domain spectroscopy

300\,^{\circ }

Intense terahertz emission from undoped GaAs/n-type GaAs and InAs/AlSb structures grown on Si substrates in the transmission-geometry excitation

300∘C), where the defect density is high, without compromising the spectral bandwidth and carrier lifetimes necessary for ultrafast THz detection. The LT-GaAs grown at